| Author | Title | Year | Journal/Proceedings | Reftype | DOI/URL |
|---|---|---|---|---|---|
| Lenz, R. & Latorre Carmona, P. | Hierarchical S(3)-Coding of RGB Histograms [BibTeX] |
2010 | Vol. 68Selected papers from VISAPP 2009, pp. 188–-200 |
incollection | |
BibTeX:
@incollection{Lenz2010,
author = {Reiner Lenz and Pedro Latorre Carmona},
title = {Hierarchical S(3)-Coding of RGB Histograms},
booktitle = {Selected papers from VISAPP 2009},
publisher = {Springer},
year = {2010},
volume = {68},
pages = {188–-200}
}
|
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| Andersson, T., Läthén, G., Lenz, R. & Borga, M. | A Fast Optimization Method for Level Set Segmentation | 2009 | Image AnalysisProceedings 16th Scandinavian Conference, SCIA 2009, pp. 400-409 | inproceedings | URL |
| Abstract: Level set methods are a popular way to solve the image segmentation problem in computer image analysis. A contour is implicitly represented by the zero level of a signed distance function, and evolved according to a motion equation in order to minimize a cost function. This function defines the objective of the segmentation problem and also includes regularization constraints. Gradient descent search is the de facto method used to solve this optimization problem. Basic gradient descent methods, however, are sensitive for local optima and often display slow convergence. Traditionally, the cost functions have been modified to avoid these problems. In this work, we instead propose using a modified gradient descent search based on resilient propagation (Rprop), a method commonly used in the machine learning community. Our results show faster convergence and less sensitivity to local optima, compared to traditional gradient descent. | |||||
BibTeX:
@inproceedings{Andersson2009,
author = {Thord Andersson and Gunnar Läthén and Reiner Lenz and Magnus Borga},
title = {A Fast Optimization Method for Level Set Segmentation},
booktitle = {Proceedings 16th Scandinavian Conference, SCIA 2009},
journal = {Image Analysis},
publisher = {Springer},
year = {2009},
pages = {400--409},
note = {Oslo, Norway, June 15-18, 2009.},
url = {http://dx.doi.org/10.1007/978-3-642-02230-2_41}
}
|
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| Läthén, G., Andersson, T., Lenz, R. & Borga, M. | Momentum Based Optimization Methods for Level Set Segmentation | 2009 | Scale Space and Variational Methods in Computer VisionProceedings Second International Conference, SSVM 2009, Voss, pp. 124-136 | inproceedings | URL |
| Abstract: Segmentation of images is often posed as a variational problem. As such, it is solved by formulating an energy functional depending on a contour and other image derived terms. The solution of the segmentation problem is the contour which extremizes this functional. The standard way of solving this optimization problem is by gradient descent search in the solution space, which typically suffers from many unwanted local optima and poor convergence. Classically, these problems have been circumvented by modifying the energy functional. In contrast, the focus of this paper is on alternative methods for optimization. Inspired by ideas from the machine learning community, we propose segmentation based on gradient descent with momentum. Our results show that typical models hampered by local optima solutions can be further improved by this approach. We illustrate the performance improvements using the level set framework. | |||||
BibTeX:
@inproceedings{Lath'en2009,
author = {Gunnar Läthén and Thord Andersson and Reiner Lenz and Magnus Borga},
title = {Momentum Based Optimization Methods for Level Set Segmentation},
booktitle = {Proceedings Second International Conference, SSVM 2009, Voss},
journal = {Scale Space and Variational Methods in Computer Vision},
publisher = {Springer},
year = {2009},
pages = {124--136},
url = {http://dx.doi.org/10.1007/978-3-642-02256-2_11}
}
|
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| Läthén, G., Andersson, T., Lenz, R. & Borga, M. | Level set based segmentation using gradient descent with momentum [BibTeX] |
2009 | SSBA 2009, Symposium on image analysis,2009, pp. 1-4 | inproceedings | DOI URL |
BibTeX:
@inproceedings{Lath'en2009a,
author = {Läthén, Gunnar and Andersson, Thord and Lenz, Reiner and Borga, Magnus},
title = {Level set based segmentation using gradient descent with momentum},
booktitle = {SSBA 2009, Symposium on image analysis,2009},
publisher = {Halmstad University},
year = {2009},
pages = {1-4},
url = {http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-45370},
doi = {urn:nbn:se:liu:diva-45370}
}
|
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| Lenz, R. | Octahedral Filters for 3D Image Processing [BibTeX] |
2009 | Proceedings SSBA 2009, pp. 109-112 | inproceedings | |
BibTeX:
@inproceedings{Lenz2009,
author = {Reiner Lenz},
title = {Octahedral Filters for 3D Image Processing},
booktitle = {Proceedings SSBA 2009},
year = {2009},
pages = {109--112}
}
|
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| Lenz, R. & Carmona, P.L. | Transform Coding of RGB-Histograms [BibTeX] |
2009 | International Conference on Computer Vision Theory and Applications (VISAPP), pp. 117-124 | inproceedings | URL |
BibTeX:
@inproceedings{Lenz2009a,
author = {Reiner Lenz and Pedro Latorre Carmona},
title = {Transform Coding of RGB-Histograms},
booktitle = {International Conference on Computer Vision Theory and Applications (VISAPP)},
year = {2009},
pages = {117-124},
note = {ISBN: 978-989-8111-69-2},
url = {http://webstaff.itn.liu.se/~reile/prints/VisApp2009.pdf}
}
|
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| Lenz, R. & Latorre Carmona, P. | Octahedral Transforms for 3-D Image Processing | 2009 | Image Processing, IEEE Transactions on Vol. 18(12)Image Processing, IEEE Transactions on, pp. 2618-2628 |
article | URL |
| Abstract: |
|||||
BibTeX:
@article{Lenz2009b,
author = {Lenz, R. and Latorre Carmona, P.},
title = {Octahedral Transforms for 3-D Image Processing},
booktitle = {Image Processing, IEEE Transactions on},
journal = {Image Processing, IEEE Transactions on},
year = {2009},
volume = {18},
number = {12},
pages = {2618--2628},
url = {http://webstaff.itn.liu.se/~reile/prints/ieeeip-2009.pdf}
}
|
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| Lenz, R., Oshima, S., Mochizuki, R. & Chao, J. | An Invariant Metric on the Manifold of Second Order Moments [BibTeX] |
2009 | IEEE Color and Reflectance in Imaging and Computer Vision Workshop 2009 - CRICV 2009, pp. 1923-1930 | inproceedings | DOI URL |
BibTeX:
@inproceedings{Lenz2009c,
author = {Lenz, Reiner and Oshima, Satoshi and Mochizuki, Rika and Chao, Jinhui},
title = {An Invariant Metric on the Manifold of Second Order Moments},
booktitle = {IEEE Color and Reflectance in Imaging and Computer Vision Workshop 2009 - CRICV 2009},
publisher = {IEEE-Computer Society},
year = {2009},
pages = {1923--1930},
url = {http://webstaff.itn.liu.se/~reile/prints/iccv2009w_251.pdf},
doi = {urn:nbn:se:liu:diva-25579}
}
|
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| Ohshima, S., Mochizuki, R., Chao, J. & Lenz, R. | Color Reproduction Using Riemann Normal Coordinates | 2009 | Computational Color Imaging Vol. 5646Second International Workshop, CCIW 2009. Revised Selected Papers, pp. 140-149 |
inproceedings | DOI URL |
| Abstract: In this paper we use tools from Riemann geometry to construct color reproduction methods that take into account the varying color perception properties of observers. We summarize the different steps in the processing: the estimation of the discrimination thresholds, the estimation of the Riemann metric, the construction of the metric-preserving or color-difference-preserving mapping and the usage of Semantic Differentiation (SD) techniques in the evaluation. We tested the method by measuring the discrimination data for 45 observers. We illustrate the geometric properties of the color spaces obtained and show the result of the metric-preserving maps between the color space of color-normal observers and a color-weak observer. We then apply the obtained maps to produce color corrected reproductions of two natural images. | |||||
BibTeX:
@inproceedings{Ohshima2009,
author = {Ohshima, Satoshi and Mochizuki, Rika and Chao, Jinhui and Lenz, Reiner},
title = {Color Reproduction Using Riemann Normal Coordinates},
booktitle = {Second International Workshop, CCIW 2009. Revised Selected Papers},
journal = {Computational Color Imaging},
publisher = {Springer},
year = {2009},
volume = {5646},
pages = {140--149},
url = {http://webstaff.itn.liu.se/~reile/prints/cciw2009.pdf},
doi = {http://dx.doi.org/10.1007/978-3-642-03265-3_15}
}
|
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| Solli, M. & Lenz, R. | Color Harmony for Image Indexing [BibTeX] |
2009 | 2009 IEEE 12th International Conference on Computer Vision Workshops, ICCV Workshops, pp. 1885-1892 | inproceedings | DOI URL |
BibTeX:
@inproceedings{Solli2009,
author = {Solli, Martin and Lenz, Reiner},
title = {Color Harmony for Image Indexing},
booktitle = {2009 IEEE 12th International Conference on Computer Vision Workshops, ICCV Workshops},
year = {2009},
pages = {1885--1892},
url = {http://webstaff.itn.liu.se/~reile/prints/iccv2009w_246.pdf},
doi = {urn:nbn:se:liu:diva-21923}
}
|
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| Solli, M. & Lenz, R. | Visualization of large font databases [BibTeX] |
2009 | Proc. IARIGAI 2009 | inproceedings | |
BibTeX:
@inproceedings{Solli2009a,
author = {Martin Solli and Reiner Lenz},
title = {Visualization of large font databases},
booktitle = {Proc. IARIGAI 2009},
year = {2009}
}
|
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| Solli, M. & Lenz, R. | Color Based Bags-of-Emotions | 2009 | Computer Analysis of Images and Patterns Vol. 5702Proceedings Computer Analysis of Images and Patterns (CAIP 2009), pp. 573-580 |
inproceedings | DOI URL |
| Abstract: In this paper we describe how to include high level semantic information, such as aesthetics and emotions, into Content Based Image Retrieval. We present a color-based emotion-related image descriptor that can be used for describing the emotional content of images. The color emotion metric used is derived from psychophysical experiments and based on three variables: activity, weight and heat. It was originally designed for single-colors, but recent research has shown that the same emotion estimates can be applied in the retrieval of multi-colored images. Here we describe a new approach, based on the assumption that perceived color emotions in images are mainly affected by homogenous regions, defined by the emotion metric, and transitions between regions. RGB coordinates are converted to emotion coordinates, and for each emotion channel, statistical measurements of gradient magnitudes within a stack of low-pass filtered images are used for finding interest points corresponding to homogeneous regions and transitions between regions. Emotion characteristics are derived for patches surrounding each interest point, and saved in a bag-of-emotions, that, for instance, can be used for retrieving images based on emotional content. | |||||
BibTeX:
@inproceedings{Solli2009b,
author = {Solli, Martin and Lenz, Reiner},
title = {Color Based Bags-of-Emotions},
booktitle = {Proceedings Computer Analysis of Images and Patterns (CAIP 2009)},
journal = {Computer Analysis of Images and Patterns},
publisher = {Springer},
year = {2009},
volume = {5702},
pages = {573--580},
url = {http://webstaff.itn.liu.se/~reile/prints/CAIP2009.pdf},
doi = {http://dx.doi.org/10.1007/978-3-642-03767-2}
}
|
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| Chao, J., Lenz, R., Matsumoto, D. & Nakamura, T. | Riemann Geometry for Color Characterization and Mapping [BibTeX] |
2008 | Proc. CGIV 2008, pp. 277-282 | inproceedings | DOI URL |
BibTeX:
@inproceedings{Chao2008,
author = {Chao, Jinhui and Lenz, Reiner and Matsumoto, Daisuke and Nakamura, Tatsuya},
title = {Riemann Geometry for Color Characterization and Mapping},
booktitle = {Proc. CGIV 2008},
publisher = {Society for Imaging Science and Technology},
year = {2008},
pages = {277--282},
url = {http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-42580},
doi = {urn:nbn:se:liu:diva-42580}
}
|
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| Heikkinen, V., Lenz, R., Jetsu, T., Parkkinen, J. & Jääskeläinen, T. | Estimation of Reflectance Spectra Using Multiple Illuminations [BibTeX] |
2008 | Proc. CGIV 2008, pp. 272-276 | inproceedings | DOI URL |
BibTeX:
@inproceedings{Heikkinen2008,
author = {Heikkinen, Ville and Lenz, Reiner and Jetsu, Tuija and Parkkinen, Jussi and Jääskeläinen, Timo},
title = {Estimation of Reflectance Spectra Using Multiple Illuminations},
booktitle = {Proc. CGIV 2008},
publisher = {Society for Imaging Science and Technology},
year = {2008},
pages = {272--276},
url = {http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-42581},
doi = {urn:nbn:se:liu:diva-42581}
}
|
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| Heikkinen, V., Lenz, R., Jetsu, T., Parkkinen, J., Hauta-Kasari, M. & Jääskeläinen, T. | Evaluation and unification of some methods for estimating reflectance spectra from RGB images | 2008 | J. Opt. Soc. Am. A Vol. 25(10), pp. 2444-2458 |
article | URL |
| Abstract: The problem of estimating spectral reflectances from the responses of a digital camera has received considerable attention recently. This problem can be cast as a regularized regression problem or as a statistical inversion problem. We discuss some previously suggested estimation methods based on critically undersampled RGB measurements and describe some relations between them. We concentrate mainly on those models that are using a priori information in the form of high-resolution measurements. We use the “kernel machine” framework in our evaluations and concentrate on the use of multiple illuminations and on the investigation of the performance of global and locally adapted estimation methods. We also introduce a nonlinear transformation of reflectance values to ensure that the estimated reflection spectra fulfill physically motivated boundary conditions. The reported experimental results are derived from measured and simulated camera responses from the Munsell Matte, NCS, and Pantone data sets. | |||||
BibTeX:
@article{Heikkinen2008a,
author = {Heikkinen, Ville and Lenz, Reiner and Jetsu, Tuija and Parkkinen, Jussi and Hauta-Kasari, Markku and Jääskeläinen, Timo},
title = {Evaluation and unification of some methods for estimating reflectance spectra from RGB images},
journal = {J. Opt. Soc. Am. A},
publisher = {OSA},
year = {2008},
volume = {25},
number = {10},
pages = {2444--2458},
url = {http://josaa.osa.org/abstract.cfm?URI=josaa-25-10-2444}
}
|
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| Lenz, R. | Lie methods for color robot vision | 2008 | Robotica Vol. 26(4), pp. 453-464 |
article | URL |
| Abstract: We describe how Lie-theoretical methods can be used to analyze color related problems in machine vision. The basic observation is that the nonnegative nature of spectral color signals restricts these functions to be members of a limited, conical section of the larger Hilbert space of square-integrable functions. From this observation, we conclude that the space of color signals can be equipped with a coordinate system consisting of a half-axis and a unit ball with the Lorentz groups as natural transformation group. We introduce the theory of the Lorentz group SU(1, 1) as a natural tool for analyzing color image processing problems and derive some descriptions and algorithms that are useful in the investigation of dynamical color changes. We illustrate the usage of these results by describing how to compress, interpolate, extrapolate, and compensate image sequences generated by dynamical color changes. ? 2007 Cambridge University Press. | |||||
BibTeX:
@article{Lenz2008,
author = {Lenz, R.},
title = {Lie methods for color robot vision},
journal = {Robotica},
year = {2008},
volume = {26},
number = {4},
pages = {453--464},
url = {http://www.scopus.com/scopus/inward/record.url?eid=2-s2.0-47849116072&partnerID=40&rel=R8.0.0}
}
|
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| Lenz, R. | Structures in Spaces of RGB Histograms [BibTeX] |
2008 | 14. Workshop Farbbildverarbeitung, Aachen, 1.-2. Oktober 2008, pp. 13-22 | inproceedings | DOI URL |
BibTeX:
@inproceedings{Lenz2008a,
author = {Lenz, Reiner},
title = {Structures in Spaces of RGB Histograms},
booktitle = {14. Workshop Farbbildverarbeitung, Aachen, 1.-2. Oktober 2008},
publisher = {Shaker Verlag},
year = {2008},
pages = {13--22},
url = {http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-43080},
doi = {urn:nbn:se:liu:diva-43080}
}
|
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| Mochizuki, R., Nakamura, T., Chao, J. & Lenz, R. | Correction of Color-Weakness by Matching of Discrimination Thresholds [BibTeX] |
2008 | Proc. CGIV 2008, pp. 208-213 | inproceedings | DOI URL |
BibTeX:
@inproceedings{Mochizuki2008,
author = {Mochizuki, Rika and Nakamura, Tatsuya and Chao, Jinhui and Lenz, Reiner},
title = {Correction of Color-Weakness by Matching of Discrimination Thresholds},
booktitle = {Proc. CGIV 2008},
publisher = {The Society for Imaging Science and Technology},
year = {2008},
pages = {208--213},
url = {http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-42579},
doi = {urn:nbn:se:liu:diva-42579}
}
|
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| Solli, M. & Lenz, R. | Color Emotions for Image Classification and Retrieval [BibTeX] |
2008 | Proc. CGIV 2008, pp. 367-371 | inproceedings | DOI URL |
BibTeX:
@inproceedings{Solli2008,
author = {Solli, Martin and Lenz, Reiner},
title = {Color Emotions for Image Classification and Retrieval},
booktitle = {Proc. CGIV 2008},
publisher = {Society for Imaging Science and Technology},
year = {2008},
pages = {367--371},
url = {http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-42582},
doi = {urn:nbn:se:liu:diva-42582}
}
|
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| Solli, M. & Lenz, R. | Emotional Satisfaction in Color Image Retrieval [BibTeX] |
2008 | Proceedings Swedish Symposium on Image Analysis 2008, pp. 7-10 | inproceedings | |
BibTeX:
@inproceedings{Solli2008a,
author = {Solli, M. and Lenz, R.},
title = {Emotional Satisfaction in Color Image Retrieval},
booktitle = {Proceedings Swedish Symposium on Image Analysis 2008},
year = {2008},
pages = {7-10}
}
|
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| Alsam, A. & Lenz, R. | Calibrating Color Cameras using Metameric Blacks | 2007 | Journal Optical Society of America A Vol. 24(1), pp. 11-17 |
article | |
| Abstract: Spectral calibration of digital cameras based on the spectral data of commercially available calibration charts is an ill-conditioned problem that has an infinite number of solutions. We introduce a method to estimate the sensor's spectral sensitivity function based on metamers. For a given patch on the calibration chart we construct numerical metamers by computing convex linear combinations of spectra from calibration chips with lower and higher sensor response values. The difference between the measured reflectance spectrum and the numerical metamer lies in the null space of the sensor. For each measured spectrum we use this procedure to compute a collection of color signals that lie in the null space of the sensor. For a collection of such spaces we compute the robust principal components, and we obtain an estimate of the sensor by computing the common null space spanned by these vectors. Our approach has a number of advantages over standard techniques: It is robust to outliers and is not dominated by larger response values, and it offers the ability to evaluate the goodness of the solution where it is possible to show that the solution is optimal, given the data, if the calculated range is one dimensional. | |||||
BibTeX:
@article{Alsam2007,
author = {Ali Alsam and Reiner Lenz},
title = {Calibrating Color Cameras using Metameric Blacks},
journal = {Journal Optical Society of America A},
year = {2007},
volume = {24},
number = {1},
pages = {11--17}
}
|
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| Latorre Carmona, P. & Lenz, R. | Performance evaluation of dimensionality reduction techniques for multispectral images | 2007 | Int. J. Imaging Systems and Technology Vol. 17(3), pp. 202-217 |
article | DOI |
| Abstract: We consider several collections of multispectral color signals and describe how linear and nonlinear methods can be used to investigate their internal structure. We use databases consisting of blackbody radiators, approximated and measured daylight spectra, multispectral images of indoor and outdoor scenes under different illumination conditions, and numerically computed color signals. We apply principal components analysis, group-theoretical methods and three manifold learning methods: Laplacian Eigenmaps, ISOMAP, and conformal component analysis. Identification of low-dimensional structures in these databases is important for analysis, model building and compression and we compare the results obtained by applying the algorithms to the different databases. |
|||||
BibTeX:
@article{LatorreCarmona2007,
author = {Latorre Carmona, Pedro and Reiner Lenz},
title = {Performance evaluation of dimensionality reduction techniques for multispectral images},
journal = {Int. J. Imaging Systems and Technology},
year = {2007},
volume = {17},
number = {3},
pages = {202-217},
doi = {http://dx.doi.org/10.1002/ima.20107}
}
|
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| Latorre Carmona, P., Lenz, R., Pla, F. & Sotoca, J. | Affine Illumination Compensation for Multispectral Images | 2007 | Image Analysis Vol. 4522Image Analysis, 15th Scandinavian Conference, SCIA 2007, Aalborg, Denmark, June 10-14, 2007, pp. 522-531 |
inproceedings | URL |
| Abstract: We apply a general form of affine transformation model to compensate illumination variations in a series of multispectral images of a static scene and compare it to a particular affine and a diagonal transformation models. These models operate in the original multispectral space or in a lower-dimensional space obtained by Singular Value Decomposition (SVD) of the set of images. We use a system consisting of a multispectral camera and a light dome that allows the measurement of multispectral data under carefully controlled illumination conditions to generate a series of multispectral images of a static scene under varying illumination conditions. We evaluate the compensation performance using the CIELAB colour difference between images. The experiments show that the first 2 models perform satisfactorily in the original and lower dimensional spaces. | |||||
BibTeX:
@inproceedings{LatorreCarmona2007a,
author = {Latorre Carmona, Pedro and Lenz, Reiner and Pla, Filiberto and Sotoca, Jose},
title = {Affine Illumination Compensation for Multispectral Images},
booktitle = {Image Analysis, 15th Scandinavian Conference, SCIA 2007, Aalborg, Denmark, June 10-14, 2007},
journal = {Image Analysis},
publisher = {Springer},
year = {2007},
volume = {4522},
pages = {522--531},
url = {http://dx.doi.org/10.1007/978-3-540-73040-8_53}
}
|
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| Lenz, R. | Crystal vision-applications of point groups in computer vision | 2007 | Vol. 4844,Proc. Asian Conference Computer Vision ACCV 2007, pp. 744–753 |
inproceedings | |
| Abstract: We use methods from the representation theory of finite groups to construct efficient processing methods for the special geometries related to the finite subgroups of the rotation group. We motivate the use of these subgroups in computer vision, summarize the necessary facts from the representation theory and develop the basics of Fourier theory for these geometries. We illustrate its usage for data compression in applications where the processes are (on average) symmetrical with respect to these groups. We use the icosahedral group as an example since it is the largest finite subgroup of the 3D rotation group. Other subgroups with fewer group elements can be studied in exactly the same way. |
|||||
BibTeX:
@inproceedings{Lenz2007,
author = {Reiner Lenz},
title = {Crystal vision-applications of point groups in computer vision},
booktitle = {Proc. Asian Conference Computer Vision ACCV 2007},
publisher = {Springer},
year = {2007},
volume = {4844,},
pages = {744–753}
}
|
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| Lenz, R., Latorre Carmona, P. & Meer, P. | The Hyperbolic Geometry of Illumination-Induced Chromaticity Changes | 2007 | Computer Vision and Pattern Recognition, 2007. CVPR '07. IEEE Conference on, pp. 1-6 | inproceedings | DOI |
| Abstract: The non-negativity of color signals implies that they span a conical space with a hyperbolic geometry. We use perspective projections to separate intensity from chromaticity, and for 3-D color descriptors the chromatic properties are represented by points on the unit disk. Descriptors derived from the same object point but under different imaging conditions can be joined by a hyperbolic geodesic. The properties of this model are investigated using multichannel images of natural scenes and black body illuminants of different temperatures. We show, over a series of static scenes with different illuminants, how illumination changes influence the hyperbolic distances and the geodesics. Descriptors derived from conventional RGB images are also addressed. | |||||
BibTeX:
@inproceedings{Lenz2007a,
author = {Lenz, Reiner and Latorre Carmona, Pedro and Meer, Peter},
title = {The Hyperbolic Geometry of Illumination-Induced Chromaticity Changes},
booktitle = {Computer Vision and Pattern Recognition, 2007. CVPR '07. IEEE Conference on},
year = {2007},
pages = {1--6},
doi = {http://dx.doi.org/10.1109/CVPR.2007.383212}
}
|
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| Lenz, R. | Optimizing Color | 2007 | Proceedings of the Second International Workshop on Image Media Quality and its Applications, pp. 64-69 | inproceedings | |
| Abstract: Non-negative color signals are all located in a conical section of a function space. We use the geometrical properties of this conical space to describe chromaticity changes by differential equations related to the Lorentz group SU(1,1). After a short summary of the necessary mathematical background we illustrate the properties of this model using multichannel images of natural scenes and black body illuminants of different temperatures. We show how the parameters of the differential equations can be extracted from multispectral and RGB measurements. We illustrate the application of the model by showing how to compress highdimensional multispectral data, how to compensate illumination changes and how to simulate the effects of illumination changes. |
|||||
BibTeX:
@inproceedings{Lenz2007b,
author = {Reiner Lenz},
title = {Optimizing Color},
booktitle = {Proceedings of the Second International Workshop on Image Media Quality and its Applications},
year = {2007},
pages = {64--69},
note = {ISBN 4-9902707-2-X C3855}
}
|
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| Solli, M. & Lenz, R. | FyFont: Find-your-Font in Large Font Databases | 2007 | Image Analysis Vol. 4522Image Analysis, 15th Scandinavian Conference, SCIA 2007, Aalborg, Denmark, June 10-14, 2007, pp. 432-441 |
inproceedings | URL |
| Abstract: A search engine for font recognition in very large font data-bases is presented and evaluated. The search engine analyzes an image of a text line, and responds with the name of the font used when writing the text. After segmenting the input image into single characters, the recognition is mainly based on eigenimages calculated from edge filtered character images. We evaluate the system with printed and scanned text lines and character images. The database used contains 2763 different fonts from the English alphabet. Our evaluation shows that for 99.8 % of the queries, the correct font name is one of the five best matches. Apart from finding fonts in large databases, the search engine can also be used as a pre-processor for Optical Character Recognition. | |||||
BibTeX:
@inproceedings{Solli2007,
author = {Solli, Martin and Lenz, Reiner},
title = {FyFont: Find-your-Font in Large Font Databases},
booktitle = {Image Analysis, 15th Scandinavian Conference, SCIA 2007, Aalborg, Denmark, June 10-14, 2007},
journal = {Image Analysis},
publisher = {Springer},
year = {2007},
volume = {4522},
pages = {432--441},
url = {http://dx.doi.org/10.1007/978-3-540-73040-8_44}
}
|
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| Solli, M. & Lenz, R. | HOW TO FIND THE FONT NAME FOR THIS TITLE [BibTeX] |
2007 | Proc. Swedish Symposium in Image Analysis, pp. 37-40 | inproceedings | |
BibTeX:
@inproceedings{Solli2007a,
author = {Martin Solli and Reiner Lenz},
title = {HOW TO FIND THE FONT NAME FOR THIS TITLE},
booktitle = {Proc. Swedish Symposium in Image Analysis},
year = {2007},
pages = {37--40}
}
|
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| Alsam, A. & Lenz, R. | Calibrating Color Cameras Using Metameric Blacks | 2006 | Proc. Third European Conference on Color in Graphics, Imaging and Vision, pp. 75-80 | inproceedings | |
| Abstract: Spectral calibration of digital cameras based on the spectral data of commercially available calibration charts is an illconditioned problem which has an infinite number of solutions. To improve upon the estimate, different constraints are commonly employed. Traditionally such constraints include: nonnegativity, smoothness, uni-modality and that the estimated sensors results in as good as possible response fit. In this paper, we introduce a novel method to solve a general ill-conditioned linear system with special focus on the solution of spectral calibration. We introduce a new approach based on metamerism. We observe that the difference between two metamers (spectra that integrate to the same sensor response) is in the null-space of the sensor. These metamers are used to robustly estimate the sensor’s null-space. Based on this nullspace, we derive projection operators to solve for the range of the unknown sensor. Our new approach has a number of advantages over standard techniques: It involves no minimization which means that the solution is robust to outliers and is not dominated by larger response values. It also offers the ability to evaluate the goodness of the solution where it is possible to show that the solution is optimal, given the data, if the calculated range is one dimensional. When comparing the new algorithm with the truncated singular value decomposition and Tikhonov regularization we found that the new method performs slightly better for the training set with noticeable improvements for the test data. |
|||||
BibTeX:
@inproceedings{Alsam2006,
author = {Ali Alsam and Reiner Lenz},
title = {Calibrating Color Cameras Using Metameric Blacks},
booktitle = {Proc. Third European Conference on Color in Graphics, Imaging and Vision},
publisher = {IS&T: The Society for Imaging Science and Technology, 7003 Kilworth Lane, Springfield, VA 22151 USA, info@imaging.org; www.imaging.org},
year = {2006},
pages = {75--80},
note = {Leeds, UK}
}
|
|||||
| Bui, T., Lenz, R. & Solli, M. | Illumination Induced Changes in Image Statistics | 2006 | Proc. Third European Conference on Color in Graphics, Imaging and Vision, pp. 48-53 | inproceedings | |
| Abstract: We have previously shown that it is possible to construct a coordinate system in the space of illumination spectra such that the coordinate vectors of the illuminants are located in a cone. Changes in the space of illuminants can then be described by an intensity related scaling and a transformation in the Lorentz group SU(1,1). In practice it is often difficult and expensive to measure these coordinate vectors. Therefore it is of interest to estimate the characteristics of an illuminant from an RGB image captured by a camera. In this paper we will investigate the relation between sequences of illuminants and statistics computed from RGB images of scenes illuminated by these illuminants. As a typical example we will study sequences of black body radiators of varying temperature. We have shown earlier that black body radiators in the mired parametrization can be described by one-parameter groups of the Lorentz group SU(1,1). In this paper we will show that this group theoretical structure of the illuminant space induces a similar structure in spaces of statistical descriptors of the resulting RGB images. We show this relation for mean vectors of RGB images, for RGB histograms and for histograms of images obtained by applying certain spatiospectral linear filters to the RGB images. As a result we obtain estimates of the color temperature of the illuminant from sequences of RGB images of scenes under these illuminants. |
|||||
BibTeX:
@inproceedings{Bui2006,
author = {Thanh Bui and Reiner Lenz and Martin Solli},
title = {Illumination Induced Changes in Image Statistics},
booktitle = {Proc. Third European Conference on Color in Graphics, Imaging and Vision},
publisher = {IS&T: The Society for Imaging Science and Technology, 7003 Kilworth Lane, Springfield, VA 22151 USA, info@imaging.org; www.imaging.org},
year = {2006},
pages = {48--53},
note = {Leeds, UK}
}
|
|||||
| Lenz, R. & Solli, M. | Lie Methods in Color Signal Processing: Illumination Effects [BibTeX] |
2006 | Vol. IIIProc. ICPR 2006,Hongkong, pp. 738-741 |
inproceedings | URL |
BibTeX:
@inproceedings{Lenz2006,
author = {R. Lenz and M. Solli},
title = {Lie Methods in Color Signal Processing: Illumination Effects},
booktitle = {Proc. ICPR 2006,Hongkong},
publisher = {IEEE-Press},
year = {2006},
volume = {III},
pages = {738-741},
url = {http://webstaff.itn.liu.se/~reile/prints/icpr-2006.pdf}
}
|
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| Bui, T.H., Lenz, R. & Kruse, B. | Color and Texture Induced Structures of Keyword Space [BibTeX] |
2005 | Vol. 2Proceedings. of 10th Congress of the International Colour Association, pp. 1059-1062 |
inproceedings | |
BibTeX:
@inproceedings{Bui2005,
author = {Thanh Hai Bui and Reiner Lenz and Björn Kruse},
title = {Color and Texture Induced Structures of Keyword Space},
booktitle = {Proceedings. of 10th Congress of the International Colour Association},
year = {2005},
volume = {2},
pages = {1059--1062}
}
|
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| Bui, T.H. | Group-Theoretical Structure in Multispectral Color and Image Databases | 2005 | Linköping studies in science and technology. Dissertations, ISSN 0345-7524 ; 962, pp. 1-193School: Linköping University | phdthesis | URL |
| Abstract: Many applications lead to signals with nonnegative function values. Understanding the structure of the spaces of nonnegative signals is therefore of interest in many different areas. Hence, constructing effective representation spaces with suitable metrics and natural transformations is an important research topic. In this thesis, we present our investigations of the structure of spaces of nonnegative signals and illustrate the results with applications in the fields of multispectral color science and content-based image retrieval. The infinite-dimensional Hilbert space of nonnegative signals is conical and convex. These two properties are preserved under linear projections onto lower dimensional spaces. The conical nature of these coordinate vector spaces suggests the use of hyperbolic geometry. The special case of three-dimensional hyperbolic geometry leads to the application of the SU(1,1) or SO 2,1) groups. We introduce a new framework to investigate nonnegative signals. We use PCA-based coordinates and apply group theoretical tools to investigate sequences of signal coordinate vectors. We describe these sequences with oneparameter subgroups of SU(1,1) and show how to compute the one-parameter subgroup of SU(1,1) from a given set of nonnegative signals. In our experiments we investigate the following signal sequences: (i) blackbody radiation spectra; (ii) sequences of daylight/twilight spectra measured in Norrk¨oping, Sweden and in Granada, Spain; (iii) spectra generated by the SMARTS2 simulation program; and (iv) sequences of image histograms. The results show that important properties of these sequences can be modeled in this framework. We illustrate the usefulness with examples where we derive illumination invariants and introduce an efficient visualization implementation. Content-Based Image Retrieval (CBIR) is another topic of the thesis. In such retrieval systems, images are first characterized by descriptor vectors. Retrieval is then based on these content-based descriptors. Selection of contentbased descriptors and defining suitable metrics are the core of any CBIR system. We introduce new descriptors derived by using group theoretical tools. We exploit the symmetry structure of the space of image patches and use the group theoretical methods to derive low-level image filters in a very general framework. The derived filters are simple and can be used for multispectral images and images defined on different sampling grids. These group theoretical filters are then used to derive content-based descriptors, which will be used in a real implementation of a CBIR. |
|||||
BibTeX:
@phdthesis{Bui2005a,
author = {Thanh Hai Bui},
title = {Group-Theoretical Structure in Multispectral Color and Image Databases},
booktitle = {Linköping studies in science and technology. Dissertations, ISSN 0345-7524 ; 962},
publisher = {Linköping University, Department of Science and Technology},
school = {Linköping University},
year = {2005},
pages = {1--193},
url = {http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-3818}
}
|
|||||
| Lenz, R., Bui, T.H. & Takase, K. | A Group Theoretical Toolbox for Color Image Operators [BibTeX] |
2005 | Proc. ICIP 05, pp. III-557-III-560 | inproceedings | |
BibTeX:
@inproceedings{Lenz2005,
author = {Reiner Lenz and Thanh Hai Bui and Koichi Takase},
title = {A Group Theoretical Toolbox for Color Image Operators},
booktitle = {Proc. ICIP 05},
year = {2005},
pages = {III-557-III-560}
}
|
|||||
| Lenz, R., Bui, T.H. & Takase, K. | Fast Low-Level Filter Systems for Multispectral Color Images [BibTeX] |
2005 | Vol. 1Proceedings. of 10th Congress of the International Colour Association, pp. 535-538 |
inproceedings | |
BibTeX:
@inproceedings{Lenz2005a,
author = {Reiner Lenz and Thanh Hai Bui and Koichi Takase},
title = {Fast Low-Level Filter Systems for Multispectral Color Images},
booktitle = {Proceedings. of 10th Congress of the International Colour Association},
year = {2005},
volume = {1},
pages = {535--538}
}
|
|||||
| Lenz, R. | Spectral Color Spaces: Their Structure and Transformations [BibTeX] |
2005 | Vol. 138Advances in imaging and electron physics, pp. 1-67 |
incollection | URL |
BibTeX:
@incollection{Lenz2005b,
author = {Reiner Lenz},
title = {Spectral Color Spaces: Their Structure and Transformations},
booktitle = {Advances in imaging and electron physics},
publisher = {Elsevier},
year = {2005},
volume = {138},
pages = {1--67},
url = {http://webstaff.itn.liu.se/~reile/prints/aiep.pdf}
}
|
|||||
| Lenz, R., Hai Bui, T. & Hernandez-Andres, J. | Group Theoretical Structure of Spectral Spaces [BibTeX] |
2005 | Journal of Mathematical Imaging and Vision Vol. 23(3), pp. 297-313 |
article | URL |
BibTeX:
@article{Lenz2005c,
author = {Lenz, Reiner and Hai Bui, Thanh and Hernandez-Andres, Javier},
title = {Group Theoretical Structure of Spectral Spaces},
journal = {Journal of Mathematical Imaging and Vision},
year = {2005},
volume = {23},
number = {3},
pages = {297--313},
url = {http://webstaff.itn.liu.se/~reile/prints/jmiv-2005.pdf}
}
|
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| Lenz, R. & Bui, T. | Statistical properties of color-signal spaces | 2005 | Journal of the Optical Society of America A (Optics, Image Science and Vision) Vol. 22(5)J. Opt. Soc. Am. A, Opt. Image Sci. Vis. (USA), pp. 820-7 |
article | URL |
| Abstract: In applications of principal component analysis (PCA) it has often been observed that the eigenvector with the largest eigenvalue has only nonnegative entries when the vectors of the underlying stochastic process have only nonnegative values. This has been used to show that the coordinate vectors in PCA are all located in a cone. We prove that the nonnegativity of the first eigenvector follows from the Perron-Frobenius (and Krein-Rutman theory). Experiments show also that for stochastic processes with nonnegative signals the mean vector is often very similar to the first eigenvector. This is not true in general, but we first give a heuristical explanation why we can expect such a similarity. We then derive a connection between the dominance of the first eigenvalue and the similarity between the mean and the first eigenvector and show how to check the relative size of the first eigenvalue without actually computing it. In the last part of the paper we discuss the implication of theoretical results for multispectral color processing | |||||
BibTeX:
@article{Lenz2005d,
author = {Lenz, R. and Bui, T.H.},
title = {Statistical properties of color-signal spaces},
booktitle = {J. Opt. Soc. Am. A, Opt. Image Sci. Vis. (USA)},
journal = {Journal of the Optical Society of America A (Optics, Image Science and Vision)},
publisher = {Opt. Soc. America},
year = {2005},
volume = {22},
number = {5},
pages = {820--7},
url = {http://webstaff.itn.liu.se/~reile/prints/josaa-2005.pdf}
}
|
|||||
| Solli, M., Andersson, M., Kruse, B. & Lenz, R. | Digital Camera Characterization for Color Measurements [BibTeX] |
2005 | 2005 Beijing International Conference on Imaging: Technology and Applications for the 21st Century, pp. 278-279 |
inproceedings | |
BibTeX:
@inproceedings{Solli2005,
author = {Martin Solli and Mattias Andersson and Björn Kruse and Reiner Lenz},
title = {Digital Camera Characterization for Color Measurements},
booktitle = {2005 Beijing International Conference on Imaging: Technology and |
|||||
| Solli, M., Andersson, M., Lenz, R. & Kruse, B. | Color Measurements with a Consumer Digital Camera Using Spectral Estimation Techniques |
2005 | Vol. 3540Proc. Scandinavian Conference Image Analysis 2005, pp. 105-114 |
inproceedings | URL |
| Abstract: The use of spectrophotometers for color measurements on printed substrates is widely spread among paper producers as well as within the printing industry. Spectrophotometer measurements are precise, but time-consuming procedures and faster methods are desirable. The rapid development of digital cameras has opened the possibility to use consumer digital cameras as substitutes for spectrophotometers for certain applications such as production control. Two methods for estimating the reflectance properties of objects from camera RGB measurements using linear estimation techniques combined with linear and non-linear constraints are presented. In the experiments, we have investigated if these techniques can be used to measure the reflectance properties of flat objects such as printed pages of paper. Reflectances were converted to CIELAB color values, and the minimization of color errors were evaluated with CIE color difference formulas. Our experiments show that a consumer digital camera can be used as a fast and inexpensive alternative to spectrophotometers for color measurements on printed substrates. |
|||||
BibTeX:
@inproceedings{Solli2005a,
author = {Martin Solli and Mattias Andersson and Reiner Lenz and Björn Kruse},
title = {Color Measurements with a Consumer Digital Camera Using Spectral |
|||||
| Tran, L.V. & Lenz, R. | Kernel Density Estimators for Hue Based Image Retrieval | 2005 | Journal Imaging Science and Technology Vol. 49(2), pp. 185-188 |
article | |
| Abstract: Color is widely used for content-based image retrieval. In these applications the color properties of an image are characterized by the probability distribution of the colors in the image. These probability distributions are very often estimated by histograms although the histograms have many drawbacks compared to other estimators such as kernel density methods. In this article we investigate whether using kernel density estimators instead of histograms could give better retrieval results based on hue descriptors of color images. In this article we introduce the Fourier series coefficients as descriptors of hue distributions. We argue that under certain conditions these coefficients are optimal in a least squared error sense. We will also apply Parseval formula to compute the similarity of two distributions directly from these Fourier coefficients. Our experiments show that this modification of the kernel based similarity estimation has better retrieval performance than the histogram methods and we will also show that the method is insensitive to parameter changes as long as they are selected in a reasonable range. |
|||||
BibTeX:
@article{Tran2005,
author = {Linh Viet Tran and Reiner Lenz},
title = {Kernel Density Estimators for Hue Based Image Retrieval},
journal = {Journal Imaging Science and Technology},
year = {2005},
volume = {49},
number = {2},
pages = {185--188}
}
|
|||||
| Tran, L.V. & Lenz, R. | Compact colour descriptors for colour-based image retrieval | 2005 | Signal Processing Vol. 85(2), pp. 233-246 |
article | URL |
| Abstract: In many colour-based image retrieval systems the colour properties of an image are described by its colour histogram. Histogram-based search is, however, often inefficient for large histogram sizes. Therefore we introduce several new, Karhunen-Loeve transform (KLT)-based methods that provide efficient representations of colour histograms and differences between two colour histograms. The methods are based on the following two observations; Ordinary KLT considers colour histograms as signals and uses the Euclidian distance for optimization; KLT with generalized colour distance measures that take into account both the statistical properties of the image database and the properties of the underlying colour space should improve the retrieval performance. Image retrieval applications compare similarities between different images. Relevant for the decision is only the local structure of the image space around the current query image since the task is to find those images in the database that are most similar to this given query image. Therefore only the local topology of the feature space is of interest and compression methods should preserve this local topology as much as possible. It is therefore more important to have a good representation of the differences between features of similar images than good representations of the features of the images themselves. The optimization should therefore be based on minimizing the approximation error in the space of local histogram differences instead of the space of colour histograms. In this paper we report the results of our experiments that are done on three image databases containing more than 130,000 images. Both objective and subjective ground truth queries are used in order to evaluate the proposed methods and to compare them with other existing methods. The results from our experiments show that compression methods based on a combination of the two observations described above provide new, powerful and efficient retrieval algorithms for colour-based image retrieval. |
|||||
BibTeX:
@article{Tran2005a,
author = {Tran, Linh Viet and Lenz, Reiner},
title = {Compact colour descriptors for colour-based image retrieval},
journal = {Signal Processing},
year = {2005},
volume = {85},
number = {2},
pages = {233--246},
url = {http://www.sciencedirect.com/science/article/B6V18-4DNR8GW-1/2/0a75efbfb1913e5ce2dd58a3f8f3c34f}
}
|
|||||
| Bui, T.H., Lenz, R. & Landelius, T. | Group theoretical investigations of daylight spectra [BibTeX] |
2004 | CGIV 2004: The Second European Conference on Colour Graphics, Imaging and Vision, pp. 437-442 | inproceedings | |
BibTeX:
@inproceedings{Bui2004,
author = {Bui, Thanh Hai and Lenz, Reiner and Landelius, Tomas},
title = {Group theoretical investigations of daylight spectra},
booktitle = {CGIV 2004: The Second European Conference on Colour Graphics, Imaging and Vision},
publisher = {IS&T},
year = {2004},
pages = {437--442}
}
|
|||||
| Lenz, R. | Time-Frequency Analysis of Color Spectra [BibTeX] |
2004 | CGIV 2004: The Second European Conference on Colour Graphics, Imaging and Vision, pp. 499-504 | inproceedings | |
BibTeX:
@inproceedings{Lenz2004,
author = {Lenz, Reiner},
title = {Time-Frequency Analysis of Color Spectra},
booktitle = {CGIV 2004: The Second European Conference on Colour Graphics, Imaging and Vision},
publisher = {IS&T},
year = {2004},
pages = {499--504}
}
|
|||||
| Lenz, R. & Hernandez-Andres, J. | Time-Frequency Analysis for Multi-Channel Color Pattern Recognition [BibTeX] |
2004 | CGIV 2004: The Second European Conference on Colour Graphics, Imaging and Vision, pp. 509-514 | inproceedings | |
BibTeX:
@inproceedings{Lenz2004a,
author = {Reiner Lenz and Javier Hernandez-Andres},
title = {Time-Frequency Analysis for Multi-Channel Color Pattern Recognition},
booktitle = {CGIV 2004: The Second European Conference on Colour Graphics, Imaging and Vision},
publisher = {IS&T},
year = {2004},
pages = {509--514}
}
|
|||||
| Lenz, R. | Color Signal Processing [BibTeX] |
2004 | Den 13. Danske Konference i Mřnstergenkendelse og Billedanalyse, pp. 2-12 | inproceedings | |
BibTeX:
@inproceedings{Lenz2004b,
author = {Lenz, Reiner},
title = {Color Signal Processing},
booktitle = {Den 13. Danske Konference i Mřnstergenkendelse og Billedanalyse},
publisher = {Datalogisk Institut, Universitetsparken 1, DK-2100 Copenhagen, Denmark |
|||||
| Lenz, R. & Bui, T. | Recognition of non-negative patterns | 2004 | Vol. Vol.3Proceedings of the 17th International Conference on Pattern Recognition, pp. 498-501 |
inproceedings | |
| Abstract: Principal component analysis (PCA) is one of the most important and popular tools used to recognize and compress patterns. The principal components are the basis functions that minimize the mean-squared error and they can be used as matched filters. In many PCA applications it has been observed that the eigenvector with the largest eigenvalue has only non-negative entries when the vectors of the underlying stochastic process have only non-negative values. This has been used to show that the coordinate vectors in PCA are all located in a cone. This in turn can be used to construct invariants, for tracking or compression. In this paper we show how this empirical observation can be rigorously proved. For the case of patterns described by vectors we use the Perron-Frobenius theory of non-negative matrices to investigate stochastic processes of finite-dimensional patterns that assume only non-negative function values. We show that they always have a first eigenfunction that assumes only non-negative values. We also describe the conditions under which the first eigenfunction has strictly positive values. For stochastic processes of patterns in Hilbert (or Banach) spaces we use versions of the Krein-Rutman theory to prove the non-negativity of the first eigenfunction. In contrast to the finite-dimensional case we see that this formulation gives a more direct connection to the conical structure of the underlying pattern space. As a concrete example we sketch how these results can be used in multi-spectral color processing | |||||
BibTeX:
@inproceedings{Lenz2004c,
author = {Lenz, R. and Bui, T.H.},
title = {Recognition of non-negative patterns},
booktitle = {Proceedings of the 17th International Conference on Pattern Recognition},
publisher = {IEEE Comput. Soc},
year = {2004},
volume = {Vol.3},
pages = {498--501}
}
|
|||||
| Olsson, B., Ynnerman, A. & Lenz, R. | Visualizing weather with synthetic high dynamic range images [BibTeX] |
2004 | Proc. SPIE-2004, Visualization and Data Analysis 2004, San Jose, USA | inproceedings | |
BibTeX:
@inproceedings{Olsson2004,
author = {B. Olsson and A. Ynnerman and R. Lenz},
title = {Visualizing weather with synthetic high dynamic range images},
booktitle = {Proc. SPIE-2004, Visualization and Data Analysis 2004, San Jose, USA},
year = {2004}
}
|
|||||
| Olsson, B., Ynnerman, A. & Lenz, R. | Computing synthetic satellite images from weather prediction data [BibTeX] |
2004 | Proc. SPIE-2004, Visualization and Data Analysis 2004, San Jose, USA |
inproceedings | |
BibTeX:
@inproceedings{Olsson2004a,
author = {B. Olsson and A. Ynnerman and R. Lenz},
title = {Computing synthetic satellite images from weather prediction data},
booktitle = {Proc. SPIE-2004, Visualization and Data Analysis 2004, San Jose, |
|||||
| Tran, L.V. & Lenz, R. | Efficient Descriptors of Hue Distributions from Kernel Density Estimators and Fourier Transforms [BibTeX] |
2004 | CGIV 2004: The Second European Conference on Colour Graphics, Imaging and Vision, pp. 151-155 |
inproceedings | |
BibTeX:
@inproceedings{Tran2004,
author = {Linh Viet Tran and Reiner Lenz},
title = {Efficient Descriptors of Hue Distributions from Kernel Density Estimators |
|||||
| Bui, T.H. | Non-Euclidean structures in PCA-based descriptions of multispectral databases [BibTeX] |
2003 | School: Linköping University | phdthesis | |
BibTeX:
@phdthesis{Bui2003,
author = {Thanh Hai Bui},
title = {Non-Euclidean structures in PCA-based descriptions of multispectral databases},
school = {Linköping University},
year = {2003},
note = {ISBN/ISSN: 9173737666}
}
|
|||||
| Lenz, R., Tran, L.V. & Bui, T.H. | Group Theoretical Invariants in Color Image Processing [BibTeX] |
2003 | Proc. Eleventh Color Imaging Conference, pp. 212-217 | inproceedings | |
BibTeX:
@inproceedings{Lenz2003,
author = {Reiner Lenz and Linh Viet Tran and Thanh Hai Bui},
title = {Group Theoretical Invariants in Color Image Processing},
booktitle = {Proc. Eleventh Color Imaging Conference},
year = {2003},
pages = {212--217}
}
|
|||||
| Lenz, R. & Bui, T.H. | Efficient Descriptors of Hue Distributions from Kernel Density Estimators and Fourier Transforms [BibTeX] |
2003 | Proc. Swedish Society for Automated Image Analysis | inproceedings | |
BibTeX:
@inproceedings{Lenz2003a,
author = {Reiner Lenz and Thanh Hai Bui},
title = {Efficient Descriptors of Hue Distributions from Kernel Density Estimators |
|||||
| Lenz, R., Bui, T. & Hernandez-Andres, J. | One-parameter subgroups and the chromaticity properties of time-changing illumination spectra | 2003 | Vol. 5008Proc. SPIE - Int. Soc. Opt. Eng. (USA), pp. 237-48 |
inproceedings | |
| Abstract: Understanding the properties of time-varying illumination spectra is of importance in all applications where dynamical color changes due to changes in illumination characteristics have to be analyzed or synthesized. Examples are (dynamical) color constancy and the creation of realistic animations. We show how group theoretical methods can be used to describe sequences of time changing illumination spectra with only few parameters. From the description we can also derive a differential equation that describes the illumination changes. We illustrate the method with investigations of black-body radiation and measured sequences of daylight spectra | |||||
BibTeX:
@inproceedings{Lenz2003b,
author = {Lenz, R. and Bui, T.H. and Hernandez-Andres, J.},
title = {One-parameter subgroups and the chromaticity properties of time-changing illumination spectra},
booktitle = {Proc. SPIE - Int. Soc. Opt. Eng. (USA)},
publisher = {SPIE-Int. Soc. Opt. Eng},
year = {2003},
volume = {5008},
pages = {237--48}
}
|
|||||
| Lenz, R. & Bui, T.H. | Illumination Invariants [BibTeX] |
2003 | Proc. PICS-2003, pp. 506-511 | inproceedings | |
BibTeX:
@inproceedings{Lenz2003c,
author = {Reiner Lenz and Thanh Hai Bui},
title = {Illumination Invariants},
booktitle = {Proc. PICS-2003},
year = {2003},
pages = {506-511}
}
|
|||||
| Olsson, B., Ynnerman, A. & Lenz, R. | SkyVis, an application of Matlab in meteorological visualization [BibTeX] |
2003 | Nordic Matlab Conference, Copenhagen | inproceedings | |
BibTeX:
@inproceedings{Olsson2003,
author = {B. Olsson and A. Ynnerman and R. Lenz},
title = {SkyVis, an application of Matlab in meteorological visualization},
booktitle = {Nordic Matlab Conference, Copenhagen},
year = {2003}
}
|
|||||
| Olsson, B., Ynnerman, A. & Lenz, R. | Eigenskies: a method of visualizing weather prediction data | 2003 | Vol. 5009Proc. SPIE - Int. Soc. Opt. Eng. (USA), pp. 1-10 |
inproceedings | |
| Abstract: Visualizing a weather prediction data set by actually synthesizing an image of the sky is a difficult problem. In this paper we present a method for synthesizing realistic sky images from weather prediction and climate prediction data. Images of the sky are combined with a number of weather parameters (like pressure and temperature) to train an artificial neural network (ANN) to predict the appearance of the sky from certain weather parameters. Hourly measurements from a period of eight months are used. The principal component analysis (PCA) method is used to decompose images of the sky into their eigen components - the eigenskies. In this way the image information is compressed into a small number of coefficients while still preserving the main information in the image. This means that the fine details of the cloud cover cannot be synthesized using this method. The PCA coefficients together with measured weather parameters at the same time form a data point that is used to train the ANN. The results show that the method gives adequate results and although some discrepancies exist, the main appearance is correct. It is possible to distinguish between different types of weather. A rainy day looks rainy and a sunny day looks sunny | |||||
BibTeX:
@inproceedings{Olsson2003a,
author = {Olsson, B. and Ynnerman, A. and Lenz, R.},
title = {Eigenskies: a method of visualizing weather prediction data},
booktitle = {Proc. SPIE - Int. Soc. Opt. Eng. (USA)},
publisher = {SPIE-Int. Soc. Opt. Eng},
year = {2003},
volume = {5009},
pages = {1--10}
}
|
|||||
| Tran, L. & Lenz, R. | Characterization of color distributions with histograms and kernel density estimators | 2003 | Vol. 5018Proc. SPIE - Int. Soc. Opt. Eng. (USA), pp. 179-89 |
inproceedings | |
| Abstract: Color is widely used for content-based image retrieval. In these applications the color properties of an image are characterized by the probability distribution of the colors in the image. These probability distributions are very often estimated by histograms although the histograms have many drawbacks compared to other estimators such as kernel density methods. In this paper we investigate whether using kernel density estimators instead of histograms could give better descriptors of color images. Experiments using these descriptors to estimate the parameters of the underlying color distribution and in color based image retrieval (CBIR) applications were carried out in which the MPEG71 database of 5466 color images with 50 standard queries are used as the benchmark. Noisy images are also generated and put into the CBIR application to test the robustness of the descriptors against the noise. The results of our experiments show that good density estimators are not necessarily good descriptors for CBIR applications. We found that the histograms perform better than kernel based methods when used as descriptors for CBIR applications. In the second part of the paper, optimal values of important parameters in the construction of these descriptors, particularly the smoothing parameters or the bandwidth of the estimators, are discussed. Our experiments show that using over-smoothed bandwidth gives better retrieval performance | |||||
BibTeX:
@inproceedings{Tran2003,
author = {Tran, L.V. and Lenz, R.},
title = {Characterization of color distributions with histograms and kernel density estimators},
booktitle = {Proc. SPIE - Int. Soc. Opt. Eng. (USA)},
publisher = {SPIE-Int. Soc. Opt. Eng},
year = {2003},
volume = {5018},
pages = {179--89}
}
|
|||||
| Tran, L. & Lenz, R. | Geometric invariance in describing color features | 2003 | Vol. 5008Proc. SPIE - Int. Soc. Opt. Eng. (USA), pp. 101-8 |
inproceedings | |
| Abstract: We present a projective geometry framework for color invariants using the extended dichromatic reflection model, in which more realistic and complicated illuminations are considered. Many assumptions which have been used by other methods are relaxed in our framework. Specifically some of the proposed invariants do not require any additional assumption except the ones assumed by the extended dichromatic reflection model. By putting the color invariance into the projective geometry framework, we can generate different types of invariants and clarify the assumptions under which they are valid. Experiments are presented that illustrate the results derived within our framework | |||||
BibTeX:
@inproceedings{Tran2003a,
author = {Tran, L.V. and Lenz, R.},
title = {Geometric invariance in describing color features},
booktitle = {Proc. SPIE - Int. Soc. Opt. Eng. (USA)},
publisher = {SPIE-Int. Soc. Opt. Eng},
year = {2003},
volume = {5008},
pages = {101--8}
}
|
|||||
| Viet Tran, L. | Efficient Image Retrieval with Statistical Color Descriptors | 2003 | , pp. 205School: Linköping University, Department of Science and Technology | phdthesis | URL |
| Abstract: Color has been widely used in content-based image retrieval (CBIR) applications. In such applications the color properties of an image are usually characterized by the probability distribution of the colors in the image. A distance measure is then used to measure the (dis-)similarity between images based on the descriptions of their color distributions in order to quickly find relevant images. The development and investigation of statistical methods for robust representations of such distributions, the construction of distance measures between them and their applications in efficient retrieval, browsing, and structuring of very large image databases are the main contributions of the thesis. In particular we have addressed the following problems in CBIR. Firstly, different non-parametric density estimators are used to describe color information for CBIR applications. Kernel-based methods using nonorthogonal bases together with a Gram-Schmidt procedure and the application of the Fourier transform are introduced and compared to previously used histogram-based methods. Our experiments show that efficient use of kernel density estimators improves the retrieval performance of CBIR. The practical problem of how to choose an optimal smoothing parameter for such density estimators as well as the selection of the histogram bin-width for CBIR applications are also discussed. Distance measures between color distributions are then described in a differential geometry-based framework. This allows the incorporation of geometrical features of the underlying color space into the distance measure between the probability distributions. The general framework is illustrated with two examples: Normal distributions and linear representations of distributions. The linear representation of color distributions is then used to derive new compact descriptors for color-based image retrieval. These descriptors are based on the combination of two ideas: Incorporating information from the structure of the color space with information from images and application of projection methods in the space of color distribution and the space of differences between neighboring color distributions. In our experiments we used several image databases containing more than 1,300,000 images. The experiments show that the method developed in this thesis is very fast and that the retrieval performance chievedcompares favorably with existing methods. A CBIR system has been developed and is currently available at http://www.media.itn.liu.se/cse. We also describe color invariant descriptors that can be used to retrieve images of objects independent of geometrical factors and the illumination conditions under which these images were taken. Both statistics- and physics-based methods are proposed and examined. We investigated the interaction between light and material using different physical models and applied the theory of transformation groups to derive geometry color invariants. Using the proposed framework, we are able to construct all independent invariants for a given physical model. The dichromatic reflection model and the Kubelka-Munk model are used as examples for the framework. The proposed color invariant descriptors are then applied to both CBIR, color image segmentation, and color correction applications. In the last chapter of the thesis we describe an industrial application where different color correction methods are used to optimize the layout of a newspaper page. |
|||||
BibTeX:
@phdthesis{VietTran2003,
author = {Viet Tran, Linh},
title = {Efficient Image Retrieval with Statistical Color Descriptors},
school = {Linköping University, Department of Science and Technology},
year = {2003},
pages = {205},
url = {http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-5002}
}
|
|||||
| Fayyazi, A. & Lenz, R. | Texture based Duplex-Board Layer Segmentation [BibTeX] |
2002 | Proc. Swedish Society for Automated Image Analysis | inproceedings | |
BibTeX:
@inproceedings{Fayyazi2002,
author = {A. Fayyazi and R. Lenz},
title = {Texture based Duplex-Board Layer Segmentation},
booktitle = {Proc. Swedish Society for Automated Image Analysis},
year = {2002}
}
|
|||||
| Lenz, R. | Spaces of Spectral Distributions and Their Natural Geometry [BibTeX] |
2002 | Proc. CGIV-2002, First European Conference on Colour in Graphics, Imaging and Vision, pp. 249-254 |
inproceedings | |
BibTeX:
@inproceedings{Lenz2002,
author = {Reiner Lenz},
title = {Spaces of Spectral Distributions and Their Natural Geometry},
booktitle = {Proc. CGIV-2002, First European Conference on Colour in Graphics, |
|||||
| Lenz, R. | Two Stage Principal Component Analysis of Color [BibTeX] |
2002 | IEEE Transactions Image Processing Vol. 11(6), pp. 630-635 |
article | |
BibTeX:
@article{Lenz2002a,
author = {Reiner Lenz},
title = {Two Stage Principal Component Analysis of Color},
journal = {IEEE Transactions Image Processing},
year = {2002},
volume = {11},
number = {6},
pages = {630--635}
}
|
|||||
| Lenz, R. | Li(e)ght [BibTeX] |
2002 | Proc. Swedish Society for Automated Image Analysis | inproceedings | |
BibTeX:
@inproceedings{Lenz2002b,
author = {R. Lenz},
title = {Li(e)ght},
booktitle = {Proc. Swedish Society for Automated Image Analysis},
year = {2002}
}
|
|||||
| Tran, L.V. & Lenz, R. | Color Invariant Features for Dielectric Materials [BibTeX] |
2002 | Proc. Swedish Society for Automated Image Analysis | inproceedings | |
BibTeX:
@inproceedings{Tran2002,
author = {L. V. Tran and R. Lenz},
title = {Color Invariant Features for Dielectric Materials},
booktitle = {Proc. Swedish Society for Automated Image Analysis},
year = {2002}
}
|
|||||
| Tran, L. & Lenz, R. | Spaces of probability distributions and their applications to color-based image database search | 2002 | Vol. 4421Proc. SPIE - Int. Soc. Opt. Eng. (USA), pp. 543-6 |
inproceedings | |
| Abstract: We present a framework to compute the distance between color distributions based on differential geometry. We investigate more detailed the case when color distributions are described as linear combinations of a set of pre-computed basic functions. Experiments in our color based image retrieval system, which were done on 1000 images from Corel image database, show the advantage of our method based on the new distance measure and color descriptor | |||||
BibTeX:
@inproceedings{Tran2002a,
author = {Tran, L.V. and Lenz, R.},
title = {Spaces of probability distributions and their applications to color-based image database search},
booktitle = {Proc. SPIE - Int. Soc. Opt. Eng. (USA)},
publisher = {SPIE-Int. Soc. Opt. Eng},
year = {2002},
volume = {4421},
pages = {543--6}
}
|
|||||
| Fayyazi, A. & Lenz, R. | Duplex board layer segmentation [BibTeX] |
2001 | Proc. Swedish Society for Automated Image Analysis | inproceedings | |
BibTeX:
@inproceedings{Fayyazi2001,
author = {Arash Fayyazi and Reiner Lenz},
title = {Duplex board layer segmentation },
booktitle = {Proc. Swedish Society for Automated Image Analysis},
year = {2001}
}
|
|||||
| Lenz, R. | A geometric foundation of Colorimetry [BibTeX] |
2001 | Ninth Color Imaging Conference, pp. 46-51 | inproceedings | |
BibTeX:
@inproceedings{Lenz2001,
author = {Reiner Lenz},
title = {A geometric foundation of Colorimetry},
booktitle = {Ninth Color Imaging Conference},
year = {2001},
pages = {46--51}
}
|
|||||
| Lenz, R. | Estimation of Illumination Characteristics [BibTeX] |
2001 | IEEE Transactions Image Processing Vol. 10(7), pp. 1031-1038 |
article | URL |
BibTeX:
@article{Lenz2001a,
author = {Reiner Lenz},
title = {Estimation of Illumination Characteristics},
journal = {IEEE Transactions Image Processing},
year = {2001},
volume = {10},
number = {7},
pages = {1031-1038},
url = {http://webstaff.itn.liu.se/~reile/prints/ieeeip-2001.pdf}
}
|
|||||
| Lenz, R. & Kruse, B. | NFR Ĺrsbok 2001 [BibTeX] |
2001 | Med färg i blicken | inbook | |
BibTeX:
@inbook{Lenz2001b,
author = {Reiner Lenz and Björn Kruse},
title = {NFR Ĺrsbok 2001},
booktitle = {Med färg i blicken},
publisher = {Swedish Science Press},
year = {2001}
}
|
|||||
| Lenz, R. | Colorimetry from geometry [BibTeX] |
2001 | Proc. 3rd Int. Conf. Multispectral Color Science | inproceedings | |
BibTeX:
@inproceedings{Lenz2001c,
author = {Reiner Lenz},
title = {Colorimetry from geometry},
booktitle = {Proc. 3rd Int. Conf. Multispectral Color Science},
year = {2001}
}
|
|||||
| Toivanen, P. & Lenz, R. | On distance transforms for multispectral images [BibTeX] |
2001 | Proc. 3rd Int. Conf. Multispectral Color Science | inproceedings | |
BibTeX:
@inproceedings{Toivanen2001,
author = {Pekka Toivanen and Reiner Lenz},
title = {On distance transforms for multispectral images},
booktitle = {Proc. 3rd Int. Conf. Multispectral Color Science},
year = {2001}
}
|
|||||
| Toivanen, P. & Lenz, R. | On the Properties of Gray-scale Distance Transforms [BibTeX] |
2001 | Proc. 12th Scandinavian Conference on Image Analysis | inproceedings | |
BibTeX:
@inproceedings{Toivanen2001a,
author = {P. Toivanen and R. Lenz},
title = {On the Properties of Gray-scale Distance Transforms},
booktitle = {Proc. 12th Scandinavian Conference on Image Analysis},
year = {2001}
}
|
|||||
| Tran, L.V. & Lenz, R. | PCA-based representation of color distributions for color based image retrieval [BibTeX] |
2001 | Proc. International Conference Image Processing 2001, pp. 697-700 | inproceedings | |
BibTeX:
@inproceedings{Tran2001,
author = {Linh Viet Tran and Reiner Lenz},
title = {PCA-based representation of color distributions for color based |
|||||
| Tran, L.V. & Lenz, R. | Comparison of quadratic form based color indexing methods [BibTeX] |
2001 | Proc. Swedish Society for Automated Image Analysis | inproceedings | |
BibTeX:
@inproceedings{Tran2001a,
author = {Linh Viet Tran and Reiner Lenz},
title = {Comparison of quadratic form based color indexing methods},
booktitle = {Proc. Swedish Society for Automated Image Analysis},
year = {2001}
}
|
|||||
| Yang, L., Lenz, R. & Kruse, B. | Light scattering and ink penetration effects on tone reproduction | 2001 | Journal of the Optical Society of America A (Optics, Image Science and Vision) Vol. 18(2)J. Opt. Soc. Am. A, Opt. Image Sci. Vis. (USA), pp. 360-6 |
article | |
| Abstract: Light scattering, or the so-called Yule-Nielsen effect, and ink penetration into the substrate paper play important roles in tone reproduction. We develop a framework in which the influences of both of these effects on the reflectance and tristimulus values of a halftone sample are investigated. The properties of the paper and the ink and their bilateral interaction can be parameterized by the reflectance Rp0 of the substrate paper, the transmittance Ti of the ink layer, the parameter γ describing the ink penetration, and p¯ describing the Yule-Nielsen effect. We derive explicit expressions that relate the reflectance of the ink dots (Ri), the paper (Rp) and the halftone image (R) as functions of these parameters. We also describe the optical dot gain as a function of these parameters. We further demonstrate that ink penetration leads to a decrease in optical dot gain and that scattering in the paper results in the printed image's being viewed as more saturated in color | |||||
BibTeX:
@article{Yang2001,
author = {Yang, Li and Lenz, R. and Kruse, B.},
title = {Light scattering and ink penetration effects on tone reproduction},
booktitle = {J. Opt. Soc. Am. A, Opt. Image Sci. Vis. (USA)},
journal = {Journal of the Optical Society of America A (Optics, Image Science and Vision)},
publisher = {Opt. Soc. America},
year = {2001},
volume = {18},
number = {2},
pages = {360--6}
}
|
|||||
| Hauta-Kasari, M., Wenjun, W., Miyazawa, K., Toyooka, S., Lenz, R., Parkkinen, J. & Jääskeläinen, T. | Computational Technique to Design Color Filters for Optical Pattern Recognition [BibTeX] |
2000 | Vol. 3The 9th Finnish Artificial Intelligence Conference, STeP 2000, Espoo, Finland, pp. 151-158 |
inproceedings | |
BibTeX:
@inproceedings{Hauta-Kasari2000,
author = {M. Hauta-Kasari and W. Wenjun and K. Miyazawa and S. Toyooka and |
|||||
| Lenz, R. | Color edge detectors for conical color spaces [BibTeX] |
2000 | Proc. Int. Conf. Color in Graphics an Image Processing, pp. 284-289 | inproceedings | |
BibTeX:
@inproceedings{Lenz2000,
author = {Reiner Lenz},
title = {Color edge detectors for conical color spaces},
booktitle = {Proc. Int. Conf. Color in Graphics an Image Processing},
year = {2000},
pages = {284--289}
}
|
|||||
| Lenz, R. | Lie-Theory and Dynamical Illumination Changes | 2000 | : Algebraic Frames for the Perception-Action Cycle Vol. 1888Proc. Algebraic Frames for the Perception-Action Cycle, pp. 218-228 |
inproceedings | DOI URL |
| Abstract: The description of the relation between the one-parameter groups of a group and the differential operators in the Lie-algebra of the group is one of the major topics in Lie-theory. In this paper we use this framework to derive a partial differential equation which describes the relation between the time-change of the spectral characteristics of the illumination source and the change of the color pixels in an image. In the first part of the paper we introduce and justify the usage of conical coordinate systems in color space. In the second part we derive the differential equation describing the illumination change and in the last part we illustrate the algorithm with some simulation examples. |
|||||
BibTeX:
@inproceedings{Lenz2000a,
author = {Lenz, Reiner},
title = {Lie-Theory and Dynamical Illumination Changes},
booktitle = {Proc. Algebraic Frames for the Perception-Action Cycle},
journal = {: Algebraic Frames for the Perception-Action Cycle},
publisher = {Springer Verlag},
year = {2000},
volume = {1888},
pages = {218--228},
url = {http://dx.doi.org/10.1007/10722492_16},
doi = {http://dx.doi.org/10.1007/10722492_16}
}
|
|||||
| Lenz, R. | Lie-Light tracking [BibTeX] |
2000 | Proc. Norsig 2000, pp. 379-382 | inproceedings | |
BibTeX:
@inproceedings{Lenz2000b,
author = {Reiner Lenz},
title = {Lie-Light tracking},
booktitle = {Proc. Norsig 2000},
year = {2000},
pages = {379--382}
}
|
|||||
| Lenz, R. | On Color Edge Detection [BibTeX] |
2000 | Proc. Image Processing, Image Quality, Image Capture Systems Conference, pp. 278-282 | inproceedings | |
BibTeX:
@inproceedings{Lenz2000c,
author = {Reiner Lenz},
title = {On Color Edge Detection},
booktitle = {Proc. Image Processing, Image Quality, Image Capture Systems Conference},
year = {2000},
pages = {278--282}
}
|
|||||
| Tran, L.V. & Lenz, R. | Metric structures in probability spaces: applications to color based search [BibTeX] |
2000 | Proc. Swedish Society for Automated Image Analysis, pp. 21-24 | inproceedings | |
BibTeX:
@inproceedings{Tran2000,
author = {Linh V. Tran and Reiner Lenz},
title = {Metric structures in probability spaces: applications to color based |
|||||
| Tran, L.V. & Lenz, R. | Measuring distances between color distributions [BibTeX] |
2000 | Proc. Int. Conf. Color in Graphics an Image Processing, pp. 256-260 | inproceedings | |
BibTeX:
@inproceedings{Tran2000a,
author = {Linh V. Tran and Reiner Lenz},
title = {Measuring distances between color distributions},
booktitle = {Proc. Int. Conf. Color in Graphics an Image Processing},
year = {2000},
pages = {256--260}
}
|
|||||
| Yang, L., Kruse, B. & Lenz, R. | Light Scattering and Ink Penetration Effects on Tone Reproduction [BibTeX] |
2000 | Proc. Image Processing, Image Quality, Image Capture Systems Conference, pp. 225-230 | inproceedings | |
BibTeX:
@inproceedings{Yang2000,
author = {Li Yang and Björn Kruse and Reiner Lenz},
title = {Light Scattering and Ink Penetration Effects on Tone Reproduction},
booktitle = {Proc. Image Processing, Image Quality, Image Capture Systems Conference},
year = {2000},
pages = {225--230}
}
|
|||||
| Yang, L., Kruse, B. & Lenz, R. | A framework for describing optical dot gain and ink penetration [BibTeX] |
2000 | Proc. Swedish Society for Automated Image Analysis, pp. 53-56 | inproceedings | |
BibTeX:
@inproceedings{Yang2000a,
author = {Li Yang and Björn Kruse and Reiner Lenz},
title = {A framework for describing optical dot gain and ink penetration},
booktitle = {Proc. Swedish Society for Automated Image Analysis},
year = {2000},
pages = {53--56}
}
|
|||||
| Hauta-Kasari, M., Parkkinen, J., Jaaskelainen, T. & Lenz, R. | Multi-spectral texture segmentation based on the spectral co-occurrence matrix | 1999 | Pattern Analysis and Applications Vol. 2(4)Pattern Anal. Appl. (UK), pp. 275-84 |
article | |
| Abstract: Multi-spectral images are becoming more common in industrial inspection tasks where the colour is used as a quality measure. In this paper we propose a spectral co-occurrence matrix-based method to analyse multi-spectral texture images, in which every pixel contains a measured colour spectrum. We first quantise the spectral domain of the multi-spectral images using the self-organising map. Next, we label the spectral domain according to the quantised spectra. In the spatial domain, we represent a multi-spectral texture using the spectral cooccurrence matrix, which we calculate from the labelled image. In the experimental part, we present the results of segmenting natural multi-spectral textures. We compare the k-nearest neighbour (k-NN) classifier and the multilayer perceptron neural network-based segmentation results of the multi-spectral and RGB colour textures | |||||
BibTeX:
@article{Hauta-Kasari1999,
author = {Hauta-Kasari, M. and Parkkinen, J. and Jaaskelainen, T. and Lenz, R.},
title = {Multi-spectral texture segmentation based on the spectral co-occurrence matrix},
booktitle = {Pattern Anal. Appl. (UK)},
journal = {Pattern Analysis and Applications},
publisher = {Springer-Verlag},
year = {1999},
volume = {2},
number = {4},
pages = {275--84}
}
|
|||||
| Lenz, R. & Tran, L.V. | Statistical methods for automated colour normalization and colour correction [BibTeX] |
1999 | Advances in Digital Printing | inproceedings | |
BibTeX:
@inproceedings{Lenz1999,
author = {R. Lenz and L. V. Tran},
title = {Statistical methods for automated colour normalization and colour |
|||||
| Lenz, R., Meer, P. & Hauta-Kasari, M. | Spectral-Based Illumination Estimation and Color Correction [BibTeX] |
1999 | Color Research and Application Vol. 24(2), pp. 98-111 |
article | |
BibTeX:
@article{Lenz1999a,
author = {R. Lenz and P. Meer and M. Hauta-Kasari},
title = {Spectral-Based Illumination Estimation and Color Correction},
journal = {Color Research and Application},
year = {1999},
volume = {24},
number = {2},
pages = {98--111}
}
|
|||||
| Lenz, R., Tran, L. & Meer, P. | Moment based normalization of color images [BibTeX] |
1999 | Proc. IEEE International Workshop on Multimedia Signal Processing, pp. 103-108 | inproceedings | |
BibTeX:
@inproceedings{Lenz1999b,
author = {R. Lenz and L.V. Tran and P. Meer},
title = {Moment based normalization of color images},
booktitle = {Proc. IEEE International Workshop on Multimedia Signal Processing},
year = {1999},
pages = {103--108}
}
|
|||||
| Lenz, R. & Meer, P. | Non-Euclidean structure of spectral color space | 1999 | Vol. 3826Proc. SPIE - Int. Soc. Opt. Eng. (USA), pp. 101-12 |
inproceedings | |
| Abstract: Color processing methods can be divided into methods based on human color vision and spectral based methods. Human vision based methods usually describe color with three parameters which are easy to interpret since they model familiar color perception processes. They share however the limitations of human color vision such as metamerism. Spectral based methods describe colors by their underlying spectra and thus do not involve human color perception. They are often used in industrial inspection and remote sensing. Most of the spectral methods employ a low dimensional (three to ten) representation of the spectra obtained from an orthogonal (usually eigenvector) expansion. While the spectral methods have solid theoretical foundation, the results obtained are often difficult to interpret. In this paper we show that for a large family of spectra the space of eigenvector coefficients has a natural cone structure. Thus we can define a natural, hyperbolic coordinate system whose coordinates are closely related to intensity, saturation and hue. The relation between the hyperbolic coordinate system and the perceptually uniform Lab color space is also shown. Defining a Fourier transform in the hyperbolic space can have applications in pattern recognition problems | |||||
BibTeX:
@inproceedings{Lenz1999c,
author = {Lenz, R. and Meer, P.},
title = {Non-Euclidean structure of spectral color space},
booktitle = {Proc. SPIE - Int. Soc. Opt. Eng. (USA)},
publisher = {SPIE-Int. Soc. Opt. Eng},
year = {1999},
volume = {3826},
pages = {101--12}
}
|
|||||
| Lenz, R. & Meer, P. | Über die Interpretation der Hauptachsentransformation von Farbspektren [BibTeX] |
1998 | Proc. Workshop Farbbildverarbeitung | inproceedings | |
BibTeX:
@inproceedings{Lenz1998,
author = {R. Lenz and P. Meer},
title = {Über die Interpretation der Hauptachsentransformation von Farbspektren},
booktitle = {Proc. Workshop Farbbildverarbeitung},
year = {1998}
}
|
|||||
| Lenz, R. | Steerable Filters and Invariant Recognition in Spacetime [BibTeX] |
1998 | Vol. VProc. Int. Conf. Acc. Sp. Sig. Proc. 1998, pp. 2737-2740 |
inproceedings | |
BibTeX:
@inproceedings{Lenz1998a,
author = {R. Lenz},
title = {Steerable Filters and Invariant Recognition in Spacetime},
booktitle = {Proc. Int. Conf. Acc. Sp. Sig. Proc. 1998},
publisher = {IEEE Computer Society Press},
year = {1998},
volume = {V},
pages = {2737-2740},
note = {May, 12-15, 1998, Seattle, WA, USA}
}
|
|||||
| Lenz, R. & Meer, P. | Spectral Color Representations: Color Correction, Database Search and Maximum Entropy Printing [BibTeX] |
1998 | Proc. Swedish Society for Automated Image Analysis Symposium, Uppsala, Sweden, pp. 9-12 |
inproceedings | |
BibTeX:
@inproceedings{Lenz1998b,
author = {R. Lenz and P. Meer},
title = {Spectral Color Representations: Color Correction, Database Search |
|||||
| Lenz, R. & Granlund, G. | If I had a fisheye I would not need $1,n$ or, Is hyperbolic geometry useful in image processing? [BibTeX] |
1998 | Proc. Swedish Society for Automated Image Analysis Symposium, Uppsala, Sweden, pp. 49-52 |
inproceedings | |
BibTeX:
@inproceedings{Lenz1998c,
author = {R. Lenz and G. Granlund},
title = {If I had a fisheye I would not need $1,n$ or, Is hyperbolic |
|||||
| Meer, P., Lenz, R. & Ramakrishna, S. | Efficient invariant representations [BibTeX] |
1998 | Int. J. Computer Vision Vol. 26(2), pp. 137-152 |
article | URL |
BibTeX:
@article{Meer1998,
author = {P. Meer and R. Lenz and S. Ramakrishna},
title = {Efficient invariant representations},
journal = {Int. J. Computer Vision},
year = {1998},
volume = {26},
number = {2},
pages = {137--152},
url = {http://webstaff.itn.liu.se/~reile/prints/ijcv-1998.pdf}
}
|
|||||
| Hauta-Kasari, M., Parkkinen, J., Jaaskelainen, T. & Lenz, R. | Spectral based analysis of color images [BibTeX] |
1997 | Vol. 2AIC Color 97, pp. 548-551 |
inproceedings | |
BibTeX:
@inproceedings{Hauta-Kasari1997,
author = {M. Hauta-Kasari and J. Parkkinen and T. Jaaskelainen and R. Lenz},
title = {Spectral based analysis of color images},
booktitle = {AIC Color 97},
publisher = {The Color Science Association of Japan},
year = {1997},
volume = {2},
pages = {548--551}
}
|
|||||
| Hauta-Kasari, M., Wang, W., Toyooka, S., Parkkinen, J. & Lenz, R. | Unsupervised filtering of Munsell spectra [BibTeX] |
1997 | Vol. 1Proc., The 3rd Asian Conference on Computer Vision,, pp. 248-255 |
inproceedings | |
BibTeX:
@inproceedings{Hauta-Kasari1997a,
author = {M. Hauta-Kasari and W. Wang and S. Toyooka and J. Parkkinen and R. |
|||||
| Lenz, R., Meer, P. & Hauta-Kasari, M. | Spectral-Based Illumination Estimation and Color Image Normalization [BibTeX] |
1997 | Vol. 2AIC Color 97, pp. 503-506 |
inproceedings | |
BibTeX:
@inproceedings{Lenz1997,
author = {R. Lenz and P. Meer and M. Hauta-Kasari},
title = {Spectral-Based Illumination Estimation and Color Image Normalization},
booktitle = {AIC Color 97},
publisher = {The Color Science Association of Japan},
year = {1997},
volume = {2},
pages = {503--506}
}
|
|||||
| Lenz, R. & Meer, P. | Color Image Normalization through Illuminant Recovery [BibTeX] |
1997 | Proc. Int. Conf. Accoustics Speech and Sig. Proc. 97, pp. 3141-3144 | inproceedings | |
BibTeX:
@inproceedings{Lenz1997a,
author = {R. Lenz and P. Meer},
title = {Color Image Normalization through Illuminant Recovery},
booktitle = {Proc. Int. Conf. Accoustics Speech and Sig. Proc. 97},
publisher = {IEEE Computer Society Press},
year = {1997},
pages = {3141--3144}
}
|
|||||
| Lenz, R., Meer, P. & Hauta-Kasari, M. | Spectral-Based Illumination Estimation and Color Correction [BibTeX] |
1997 | Proc. Swedish Society for Automated Image Analysis, pp. 159-163 | inproceedings | |
BibTeX:
@inproceedings{Lenz1997b,
author = {R. Lenz and P. Meer and M. Hauta-Kasari},
title = {Spectral-Based Illumination Estimation and Color Correction},
booktitle = {Proc. Swedish Society for Automated Image Analysis},
year = {1997},
pages = {159--163}
}
|
|||||
| Lenz, R., Meer, P. & Hauta-Kasari, M. | Spectral-Based Illumination Estimation and Color Correction [BibTeX] |
1997 | Proc. 10th Scandinavian Conference on Image Analysis, pp. 885-892 | inproceedings | |
BibTeX:
@inproceedings{Lenz1997c,
author = {R. Lenz and P. Meer and M. Hauta-Kasari},
title = {Spectral-Based Illumination Estimation and Color Correction},
booktitle = {Proc. 10th Scandinavian Conference on Image Analysis},
year = {1997},
pages = {885--892}
}
|
|||||
| Lenz, R. & Svanberg, J. | Group Theoretical Transforms and Statistical Properties of Image Spaces [BibTeX] |
1997 | Signal and Image Representation in Combined Spaces | incollection | |
BibTeX:
@incollection{Lenz1997d,
author = {R. Lenz and J. Svanberg},
title = {Group Theoretical Transforms and Statistical Properties of Image |
|||||
| Lenz, R. | Some applications of representations of Lie algebras and Lie groups | 1997 | : Algebraic Frames for the Perception-Action Cycle Vol. 1315/1997Algebraic Frames for the Perception-Action Cycle, pp. 114-125 |
inproceedings | DOI URL |
| Abstract: The paper gives a short overview over some basic facts from the representation theory of groups and algebras. Then we describe iterative algorithms to normalize coefficient vectors computed by expanding functions on the unit sphere into a series of spherical harmonics. Typical applications of the normalization procedure are the matching of different three-dimensional images, orientation estimations in low-level image processing or robotics. The algorithm illustrates general methods from the representation theory of Lie-groups and Lie-algebras which can be used to linearize highly-non-linear problems. It can therefore also be adapted to applications involving groups different from the group of three-dimensional rotations. The performance of the algorithm is illustrated with a few experiments involving random coefficient vectors. | |||||
BibTeX:
@inproceedings{Lenz1997e,
author = {Lenz, Reiner},
title = {Some applications of representations of Lie algebras and Lie groups},
booktitle = {Algebraic Frames for the Perception-Action Cycle},
journal = {: Algebraic Frames for the Perception-Action Cycle},
publisher = {Springer Verlag},
year = {1997},
volume = {1315/1997},
pages = {114--125},
url = {http://dx.doi.org/10.1007/BFb0017863},
doi = {http://dx.doi.org/10.1007/BFb0017857}
}
|
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| Lenz, R. & Homma, K. | Constructing iterative matching algorithms with the use of Lie theory: three-dimensional orientation example | 1997 | Journal of the Optical Society of America A (Optics, Image Science and Vision) Vol. 14(8)J. Opt. Soc. Am. A, Opt. Image Sci. Vis. (USA), pp. 1734-41 |
article | |
| Abstract: Iterative algorithms are described for normalizing-coefficient vectors computed by expanding functions on the unit sphere into a series of spherical harmonics. Typical applications of the normalization procedure are the matching of different three-dimensional images, orientation estimations in low-level image processing, or robotics. The method uses general methods from the theory of Lie groups and Lie algebras to linearize the highly nonlinear original problem and can therefore also be adapted to applications involving groups different from the group of three-dimensional rotations. The performance of the algorithm is illustrated with a few experiments involving random coefficient vectors | |||||
BibTeX:
@article{Lenz1997f,
author = {Lenz, R. and Homma, K.},
title = {Constructing iterative matching algorithms with the use of Lie theory: three-dimensional orientation example},
booktitle = {J. Opt. Soc. Am. A, Opt. Image Sci. Vis. (USA)},
journal = {Journal of the Optical Society of America A (Optics, Image Science and Vision)},
publisher = {Opt. Soc. America},
year = {1997},
volume = {14},
number = {8},
pages = {1734--41}
}
|
|||||
| Assonov, M.V., Labunets, V.G., Lenz, R. & Labunets, E. | Fast spectral algorithms for invariant pattern recognition and images matching based on modular invariants [BibTeX] |
1996 | Vol. IIIProc. International Conference Image Processing, pp. 607-610 |
inproceedings | |
BibTeX:
@inproceedings{Assonov1996,
author = {M. V. Assonov and V. G. Labunets and R. Lenz and E. Labunets},
title = {Fast spectral algorithms for invariant pattern recognition and images |
|||||
| Hauta-Kasari, M., Parkkinen, J., Jaaskelainen, T. & Lenz, R. | Generalized co-occurrence matrix for multispectral texture analysis | 1996 | Vol. vol.2Proceedings of the 13th International Conference on Pattern Recognition, pp. 785-9 |
inproceedings | |
| Abstract: We present a new co-occurrence matrix based approach for multispectral texture analysis. The spectral and spatial domains of the multispectral textures are processed separately. The color space used in this study is represented by subspaces and it is classified by the averaged learning subspace method (ALSM). In the spatial domain we use a generalized co-occurrence matrix for vector valued pixels. The texture feature vectors are classified by the k-nearest neighbor (KNN) classifier and the multilayer perceptron (MLP) network. Experimental results of the multispectral texture segmentation are presented | |||||
BibTeX:
@inproceedings{Hauta-Kasari1996,
author = {Hauta-Kasari, M. and Parkkinen, J. and Jaaskelainen, T. and Lenz, R.},
title = {Generalized co-occurrence matrix for multispectral texture analysis},
booktitle = {Proceedings of the 13th International Conference on Pattern Recognition},
publisher = {IEEE Comput. Soc. Press},
year = {1996},
volume = {vol.2},
pages = {785--9}
}
|
|||||
| Lenz, R. & Homma, K. | Rotational Symmetry: The Lie group SO(3) and its representations [BibTeX] |
1996 | Vol. IIIProc. International Conference Image Processing, pp. 203-206 |
inproceedings | |
BibTeX:
@inproceedings{Lenz1996,
author = {R. Lenz and K. Homma},
title = {Rotational Symmetry: The Lie group SO(3) and its representations},
booktitle = {Proc. International Conference Image Processing},
year = {1996},
volume = {III},
pages = {203--206}
}
|
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| Lenz, R., Österberg, M., Hiltunen, J., Jaaskelainen, T. & Parkkinen, J. | Unsupervised filtering of color spectra | 1996 | Journal of the Optical Society of America A (Optics, Image Science and Vision) Vol. 13(7)J. Opt. Soc. Am. A, Opt. Image Sci. Vis. (USA), pp. 1315-24 |
article | |
| Abstract: We describe a class of unsupervised systems that extract features from databases of reflectance spectra that sample color space in a way that reflects the properties of human color perception. The systems find the internal weight coefficients by optimizing an energy function. We describe several energy functions based on second- and fourth-order statistical moments of the computed output values. We also investigate the effects of imposing boundary conditions on the filter coefficients and the performance of the resulting systems for the databases with the reflectance spectra. The experiments show that the weight matrix for one of the systems is very similar to the eigenvector system, whereas the second type of system tries to rotate the eigenvector system in such a way that the resulting filters partition the spectrum into different bands. We also show how the system can be forced to use weight vectors with positive coefficients. Weight vectors are then approximated with Gaussian quadrature methods | |||||
BibTeX:
@article{Lenz1996a,
author = {Lenz, R. and Österberg, M. and Hiltunen, J. and Jaaskelainen, T. and Parkkinen, J.},
title = {Unsupervised filtering of color spectra},
booktitle = {J. Opt. Soc. Am. A, Opt. Image Sci. Vis. (USA)},
journal = {Journal of the Optical Society of America A (Optics, Image Science and Vision)},
publisher = {Opt. Soc. America},
year = {1996},
volume = {13},
number = {7},
pages = {1315--24}
}
|
|||||
| Lenz, R., Österberg, M., Hiltunen, J., Jaaskelainen, T. & Parkkinen, J. | Exploring color spaces with unsupervised filters and Gaussian Quadrature [BibTeX] |
1995 | Proc. Swedish Society for Automated Image Analysis, pp. 49-52 | inproceedings | |
BibTeX:
@inproceedings{Lenz1995,
author = {Reiner Lenz and Mats Österberg and Jouni Hiltunen and Timo Jaaskelainen |
|||||
| Lenz, R., Österberg, M., Hiltunen, J., Jaaskelainen, T. & Parkkinen, J. | Unsupervised Filtering of Color Spectra [BibTeX] |
1995 | Proc. Scandinavian Conf. Image Analysis, pp. 803-810 | inproceedings | |
BibTeX:
@inproceedings{Lenz1995a,
author = {Reiner Lenz and Mats Österberg and Jouni Hiltunen and Timo Jaaskelainen |
|||||
| Lenz, R. & Svanberg, J. | Group Theoretical Transforms and Their Applications in Image Coding [BibTeX] |
1995 | Proc. Int. Conf. Accoustics, Speech and Sig. Proc. | inproceedings | |
BibTeX:
@inproceedings{Lenz1995b,
author = {Reiner Lenz and Jonas Svanberg},
title = {Group Theoretical Transforms and Their Applications in Image Coding},
booktitle = {Proc. Int. Conf. Accoustics, Speech and Sig. Proc.},
year = {1995}
}
|
|||||
| Lenz, R. & Österberg, M. | Filtering: Invariance, Information Extraction and Learning [BibTeX] |
1995 | Vol. 3Progress in Neural Networks, pp. 65-98 |
inproceedings | |
BibTeX:
@inproceedings{Lenz1995c,
author = {Reiner Lenz and Mats Österberg},
title = {Filtering: Invariance, Information Extraction and Learning},
booktitle = {Progress in Neural Networks},
publisher = {Ablex Publishing Corporation},
year = {1995},
volume = {3},
pages = {65--98}
}
|
|||||
| Lenz, R. | Investigation of Receptive Fields using Representations of Dihedral Groups [BibTeX] |
1995 | Journal of Visual Communication and Image Representation Vol. 6(3), pp. 209-227 |
article | |
BibTeX:
@article{Lenz1995d,
author = {R. Lenz},
title = {Investigation of Receptive Fields using Representations of Dihedral |
|||||
| Österberg, M. & Lenz, R. | On parallel selective principal component analysis [BibTeX] |
1995 | Proc. 1995 Swedish Conference on Connectionism, pp. 67-76 | inproceedings | |
BibTeX:
@inproceedings{Osterberg1995,
author = {Mats Österberg and Reiner Lenz},
title = {On parallel selective principal component analysis},
booktitle = {Proc. 1995 Swedish Conference on Connectionism},
publisher = {Lawrence Erlbaum Ass.},
year = {1995},
pages = {67--76}
}
|
|||||
| Lenz, R. | Group Theoretical Transforms in Image Processing [BibTeX] |
1994 | Current Topics in Pattern Recognition Research,1, pp. 83-106 | incollection | |
BibTeX:
@incollection{Lenz1994,
author = {Reiner Lenz},
title = {Group Theoretical Transforms in Image Processing},
booktitle = {Current Topics in Pattern Recognition Research,1},
publisher = {Research Trends},
year = {1994},
pages = {83--106}
}
|
|||||
| Lenz, R. & Österberg, M. | Neural Networks for Unsupervised Linear Feature Extraction [BibTeX] |
1994 | Connectionism in a broad perspective, pp. 139-148 | incollection | |
BibTeX:
@incollection{Lenz1994a,
author = {Reiner Lenz and Mats Österberg},
title = {Neural Networks for Unsupervised Linear Feature Extraction},
booktitle = {Connectionism in a broad perspective},
publisher = {Ellis Horwood},
year = {1994},
pages = {139--148}
}
|
|||||
| Lenz, R. & Meer, P. | Experimental investigation of projection and permutation invariants | 1994 | Pattern Recognition Letters Vol. 15(8), pp. 751-760 |
article | URL |
| Abstract: The cross-ratio is the most popular projective invariant. It is invariant under projective transformation but it changes its value under permutation of the arguments. Using the cross-ratio it is however possible to construct invariants that are unchanged under both projections and permutations. There are three different types of these invariants: bounded rational functions, unbounded rational functions and absolute values of rational functions of the cross-ratio. All of them are equivalent under ideal, noise-free conditions. In this paper we investigate the properties of these functions under noise. | |||||
BibTeX:
@article{Lenz1994b,
author = {Lenz, Reiner and Meer, Peter},
title = {Experimental investigation of projection and permutation invariants},
journal = {Pattern Recognition Letters},
year = {1994},
volume = {15},
number = {8},
pages = {751--760},
url = {http://www.sciencedirect.com/science/article/B6V15-48M320M-92/2/71852426a9f2be72f81ffba05395f5a7}
}
|
|||||
| Lenz, R. & Meer, P. | Point configuration invariants under simultaneous projective and permutation transformations | 1994 | Pattern Recognition Vol. 27(11), pp. 1523-1532 |
article | URL |
| Abstract: The projective invariants used in computer vision today are permutation-sensitive since their value depends on the order in which the features were considered in the computation. We derive, using tools from representation theory, the projective and permutation (p2) invariants of the four collinear and the five coplanar points configurations. The p2-invariants are insensitive to both projective transformations and changes in the labeling of the points. When used as model database indexing functions in object recognition systems, the p2-invariants yield a significant speedup. Permutation invariants for affine transformations are also discussed. | |||||
BibTeX:
@article{Lenz1994c,
author = {Lenz, Reiner and Meer, Peter},
title = {Point configuration invariants under simultaneous projective and permutation transformations},
journal = {Pattern Recognition},
year = {1994},
volume = {27},
number = {11},
pages = {1523--1532},
url = {http://www.sciencedirect.com/science/article/B6V14-48MPN3T-19N/2/d0c495877762d52010646801a42dfffd}
}
|
|||||
| Meer, P., Ramakrishna, S. & Lenz, R. | Correspondence of coplanar features through $P2$-invariant representations [BibTeX] |
1994 | Lecture Notes in Computer Science Vol. 825LNCS-825, pp. 473-492 |
inproceedings | URL |
BibTeX:
@inproceedings{Meer1994,
author = {Meer, Peter and Ramakrishna, Sudhir and Lenz, Reiner},
title = {Correspondence of coplanar features through $P2$-invariant representations},
booktitle = {LNCS-825},
journal = {Lecture Notes in Computer Science},
year = {1994},
volume = {825},
pages = {473--492},
url = {http://www.springerlink.com/openurl.asp?genre=article&id=doi:10.1007/3-540-58240-1_25}
}
|
|||||
| Meer, P., Ramakrishna, S. & Lenz, R. | Correspondence of coplanar features through p2-invariant representations | 1994 | Vol. vol.1Proceedings of the 12th IAPR International Conference on Pattern Recognition (Cat. No.94CH3440-5), pp. 196-200 |
inproceedings | |
| Abstract: The correspondence between two coplanar sets of points (or lines) is established making use of a novel invariant representation of five-tuples of features. The projective/permutation (p2) invariants are insensitive to the order of the features in the computation and thus provide a significant speedup in matching. Performance degradation due to the noise sensitivity of the invariants is avoided by using context independent constraints (noncollinearity of points, preservation of the convex hull); and by accumulating the feature correspondence hypotheses in a contingency table. Full projective correspondence can be recovered reliably for positional uncertainty of several pixels or in the presence of outliers | |||||
BibTeX:
@inproceedings{Meer1994a,
author = {Meer, P. and Ramakrishna, S. and Lenz, R.},
title = {Correspondence of coplanar features through p2-invariant representations},
booktitle = {Proceedings of the 12th IAPR International Conference on Pattern Recognition (Cat. No.94CH3440-5)},
publisher = {IEEE Comput. Soc. Press},
year = {1994},
volume = {vol.1},
pages = {196--200}
}
|
|||||
| Österberg, M. & Lenz, R. | Unsupervised Parallel Feature Extraction from First Principles [BibTeX] |
1994 | Advances in Neural Information Processing Systems 6, pp. 136-144 | inproceedings | |
BibTeX:
@inproceedings{Osterberg1994,
author = {M. Österberg and R. Lenz},
title = {Unsupervised Parallel Feature Extraction from First Principles},
booktitle = {Advances in Neural Information Processing Systems 6},
publisher = {Morgan, Kaufmann},
year = {1994},
pages = {136-144}
}
|
|||||
| Österberg, M. | Quality Functions for Parallel Selective Principal Component Analysis [BibTeX] |
1994 | School: Linköping University | phdthesis | |
BibTeX:
@phdthesis{Osterberg1994a,
author = {M. Österberg},
title = {Quality Functions for Parallel Selective Principal Component Analysis},
school = {Linköping University},
year = {1994}
}
|
|||||
| Lenz, R. & Meer, P. | Projection and Permutation Invariant Object Recognition [BibTeX] |
1993 | Proc. of the 8th Scandinavian Conference on Image Analysis, pp. 389-396 | inproceedings | |
BibTeX:
@inproceedings{Lenz1993,
author = {Reiner Lenz and Peter Meer},
title = {Projection and Permutation Invariant Object Recognition},
booktitle = {Proc. of the 8th Scandinavian Conference on Image Analysis},
publisher = {NOBIM},
year = {1993},
pages = {389--396}
}
|
|||||
| Lenz, R. | Using Representations of the Dihedral Groups in the Design of Early Vision Filters [BibTeX] |
1993 | Proc. of the Swedish Society for Automated Image Analysis Symposium, Gothenburg, Sweden |
inproceedings | |
BibTeX:
@inproceedings{Lenz1993a,
author = {Reiner Lenz},
title = {Using Representations of the Dihedral Groups in the Design of Early |
|||||
| Lenz, R. | On $P^2$ Invariance [BibTeX] |
1993 | Proc. of the Swedish Society for Automated Image Analysis Symposium, Gothenburg, Sweden |
inproceedings | |
BibTeX:
@inproceedings{Lenz1993b,
author = {Reiner Lenz},
title = {On $P^2$ Invariance},
booktitle = {Proc. of the Swedish Society for Automated Image Analysis Symposium, |
|||||
| Lenz, R. | Using Representations of the Dihedral Groups in the Design of Early Vision Filters [BibTeX] |
1993 | Proc. Int. Conf. Accoustics, Speech and Sig. Proc., pp. V165-V168 | inproceedings | |
BibTeX:
@inproceedings{Lenz1993c,
author = {Reiner Lenz},
title = {Using Representations of the Dihedral Groups in the Design of Early Vision Filters},
booktitle = {Proc. Int. Conf. Accoustics, Speech and Sig. Proc.},
year = {1993},
pages = {V165-V168}
}
|
|||||
| Meer, P., Ramakrishna, S. & Lenz, R. | Indexing power of the projective/permutation invariant of five coplanar points [BibTeX] |
1993 | Applications of Invariance in Computer Vision II, pp. 133-150 | inproceedings | |
BibTeX:
@inproceedings{Meer1993,
author = {Peter Meer and Sudhir Ramakrishna and Reiner Lenz},
title = {Indexing power of the projective/permutation invariant of five coplanar |
|||||
| Seger, O. | Model building and restoration with applications in confocal microscopy [BibTeX] |
1993 | School: Linköping University | phdthesis | |
BibTeX:
@phdthesis{Seger1993,
author = {O. Seger},
title = {Model building and restoration with applications in confocal microscopy},
school = {Linköping University},
year = {1993}
}
|
|||||
| Lenz, R. & Seger, O. | Group Theoretical Methods in 3-D Image Processing [BibTeX] |
1992 | Leading Edge of Super Light Microscopy, Tokyo, 1992 | inproceedings | |
BibTeX:
@inproceedings{Lenz1992,
author = {Reiner Lenz and Olle Seger},
title = {Group Theoretical Methods in 3-D Image Processing},
booktitle = {Leading Edge of Super Light Microscopy, Tokyo, 1992},
year = {1992}
}
|
|||||
| Lenz, R. & Österberg, M. | A Method for unsupervised linear feature extraction using fourth order moments [BibTeX] |
1992 | Proc. Swedish Society for Automated Image Analysis Symposium, Uppsala, Sweden |
inproceedings | |
BibTeX:
@inproceedings{Lenz1992a,
author = {Reiner Lenz and Mats Österberg},
title = {A Method for unsupervised linear feature extraction using fourth order moments},
booktitle = {Proc. Swedish Society for Automated Image Analysis Symposium, Uppsala, |
|||||
| Lenz, R. & Seger, O. | Group Theoretical Methods in Image Science [BibTeX] |
1992 | New Trends on Scanning Optical Microscopy, OITDA Workshop, Naha, Japan, 1992 |
inproceedings | |
BibTeX:
@inproceedings{Lenz1992b,
author = {Reiner Lenz and Olle Seger},
title = {Group Theoretical Methods in Image Science},
booktitle = {New Trends on Scanning Optical Microscopy, OITDA Workshop, Naha, |
|||||
| Lenz, R. | Group Theoretical Feature Extraction: Weighted Invariance and Texture Analysis [BibTeX] |
1992 | Selected Papers from the 7th Scandinavian Conference on Image Analysis, pp. 63-70 | incollection | |
BibTeX:
@incollection{Lenz1992c,
author = {Reiner Lenz},
title = {Group Theoretical Feature Extraction: Weighted Invariance and Texture |
|||||
| Lenz, R. & Österberg, M. | Computing the Karhunen-Loéve expansion with a parallel, unsupervised filter system [BibTeX] |
1992 | Neural Computation Vol. 4, pp. 382-392 |
article | |
BibTeX:
@article{Lenz1992d,
author = {R. Lenz and M. Österberg},
title = {Computing the Karhunen-Loéve expansion with a parallel, unsupervised |
|||||
| Lenz, R. & Osterberg, M. | A new method for unsupervised linear feature extraction, using fourth-order moments | 1992 | Pattern Recognition Letters Vol. 13(12), pp. 827-836 |
article | URL |
| Abstract: In this paper we investigate an unsupervised linear feature extraction system based on the second- and fourth-order moments of the input covariance function. First we demonstrate some drawbacks of systems based on second-order moments (including all Karhunen-Loeve systems). Then we introduce a new version of our Learning filter system that is based on fourth-order moments. We show that this system has the same modular structure as our previous (second-order) systems. Then we discuss some advantages of this new system with the help of some examples. In the first example we demonstrate that this new system can detect meaningful structures even in those subspaces that belong to the same eigenvalue of the covariance matrix. Systems based on second-order moments are unable to find such structures. In the second example we train the system with two pattern sequences that have exactly the same second-order moments. We show that the system stabilizes indeed in two different states that reflect relevant properties of the whole trainings sequence. In the last example we demonstrate that the feature vectors produced by the new system are better adapted to a special type nonlinear post-processing that is motivated by the group-theoretically based filter design methodology. | |||||
BibTeX:
@article{Lenz1992e,
author = {Lenz, Reiner and Osterberg, Mats},
title = {A new method for unsupervised linear feature extraction, using fourth-order moments},
journal = {Pattern Recognition Letters},
year = {1992},
volume = {13},
number = {12},
pages = {827--836},
url = {http://www.sciencedirect.com/science/article/B6V15-48N55FK-2P/2/81aeea5074139a17b1b82e290ed3563f}
}
|
|||||
| Lenz, R. & Österberg, M. | A new method for unsupervised linear feature extraction, using fourth order moments | 1992 | Proceedings. 11th IAPR International Conference on Pattern Recognition. Vol.II. Conference B: Pattern Recognition Methodology and Systems, pp. 71-4 | inproceedings | |
| Abstract: The authors discuss two classes of unsupervised feature extraction methods. They show that a system based on second order moments can learn the Karhunen-Loeve expansion in parallel. Then they show that systems based on second order moments only have important drawbacks. The second class of systems described avoids this problem by using fourth order moments. Since these systems are much harder to analyze the authors demonstrate some of their advantages with the help of some experiments | |||||
BibTeX:
@inproceedings{Lenz1992f,
author = {Lenz, R. and Österberg, M.},
title = {A new method for unsupervised linear feature extraction, using fourth order moments},
booktitle = {Proceedings. 11th IAPR International Conference on Pattern Recognition. Vol.II. Conference B: Pattern Recognition Methodology and Systems},
publisher = {IEEE Comput. Soc. Press},
year = {1992},
pages = {71--4}
}
|
|||||
| Seger, O. & Lenz, R. | Anisotropic Image Restoration [BibTeX] |
1992 | Proc. Swedish Society for Automated Image Analysis Symposium, Uppsala, Sweden |
inproceedings | |
BibTeX:
@inproceedings{Seger1992,
author = {Olle Seger and Reiner Lenz},
title = {Anisotropic Image Restoration},
booktitle = {Proc. Swedish Society for Automated Image Analysis Symposium, Uppsala, |
|||||
| Seger, O. & Lenz, R. | Experiments with on operator model of a confocal microscope [BibTeX] |
1992 | Proc of SPIE conference on Biomedical Image Processing III and 3-D Microscopy, San Jose, USA |
inproceedings | |
BibTeX:
@inproceedings{Seger1992a,
author = {Olle Seger and Reiner Lenz},
title = {Experiments with on operator model of a confocal microscope},
booktitle = {Proc of SPIE conference on Biomedical Image Processing III and 3-D |
|||||
| Seger, O. & Lenz, R. | Modeling of the point spread function of laser scanning microscopes using canonical transforms [BibTeX] |
1992 | Journal of Visual Communication and Image Representation Vol. 3(4), pp. 364-380 |
article | |
BibTeX:
@article{Seger1992b,
author = {Olle Seger and R. Lenz},
title = {Modeling of the point spread function of laser scanning microscopes |
|||||
| Lenz, R. & Österberg, M. | A parallel learning filter system that learns the KL-expansion from examples [BibTeX] |
1991 | Proc. First IEEE-SP Workshop on Neural Networks for Signal Processing (Sept. 91) |
inproceedings | |
BibTeX:
@inproceedings{Lenz1991,
author = {Reiner Lenz and Mats Österberg},
title = {A parallel learning filter system that learns the KL-expansion from examples},
booktitle = {Proc. First IEEE-SP Workshop on Neural Networks for Signal Processing |
|||||
| Lenz, R. | Group Theoretical Feature Extraction: Weighted Invariance and Texture Analysis [BibTeX] |
1991 | Proc. Swedish Society for Automated Image Analysis Symposium, Stockholm, Sweden |
inproceedings | |
BibTeX:
@inproceedings{Lenz1991a,
author = {Reiner Lenz},
title = {Group Theoretical Feature Extraction: Weighted Invariance and Texture |
|||||
| Lenz, R. | Group Theoretical Feature Extraction: Weighted Invariance and Texture Analysis [BibTeX] |
1991 | 7th Scandinavian Conference on Image Analysis | inproceedings | |
BibTeX:
@inproceedings{Lenz1991b,
author = {Reiner Lenz},
title = {Group Theoretical Feature Extraction: Weighted Invariance and Texture |
|||||
| Lenz, R. & Österberg, M. | Learning filter systems with maximum correlation and maximum separation properties | 1991 | Vol. 1469Proc. SPIE - Int. Soc. Opt. Eng. (USA), pp. 784-95 |
inproceedings | |
| Abstract: Describe a system that can be used as a feature extraction unit in a low-level pattern recognition system. The authors assume that such a system acts as a linear mapping between the pattern space and the feature space. It can therefore be completely described by a number of filter kernels. These filter kernels are usually constructed by the designer of the system. In the approach to filter design described in the paper the authors do not create the filter kernels manually. Instead they feed the system during the trainings period with a representative selection of the patterns that they want to recognize. During the trainings phase they use a learning rule (based on a quality function) to update the current form of the filter functions | |||||
BibTeX:
@inproceedings{Lenz1991c,
author = {Lenz, R. and Österberg, M.},
title = {Learning filter systems with maximum correlation and maximum separation properties},
booktitle = {Proc. SPIE - Int. Soc. Opt. Eng. (USA)},
year = {1991},
volume = {1469},
pages = {784--95}
}
|
|||||
| Lenz, R. | On probabilistic invariance | 1991 | Neural Networks Vol. 4(5), pp. 627-641 |
article | URL |
| Abstract: The invariance principle is one important design principle in low-level pattern recognition. In the first part of this paper we investigate some theoretical aspects of this principle. In the second part we show how an adaptive filter system reacts to pattern sets that involve some kind of invariance.In its most general, group-theoretical form the invariance principle can be formulated as follows:We assume that we have a class of patterns of interest pi : i [epsilon] I and a given pattern q. The problem is to decide if q was a pattern of interest or not, i.e., if q = pi0 for some i0 [epsilon] I. If the patterns pi are generated from a common prototype pattern p0 with the help of transformations gi and if these transformations gi form a group G then this problem can be solved by finding maximum correlation filter sets. The relation between these filter sets and the prototype pattern p0 and the transformation group G is completely known.The construction of the filter functions is, however, based on the assumption that all transformations gi [epsilon] G (and therefore also all patterns pi) appear equally often. The purpose of this paper is the generalization of the filter construction process to pattern classes whose elements obey some probability distribution. In the special cases of 2-D rotation invariance and scale invariance, we will show how the maximum correlation filters depend on the prototype pattern, the transformation group, and the probability distribution. We will also sketch the theory for the case of arbitrary compact transformation groups and what type of problems turn up in this case.In the last part of the paper we describe an adaptive filter system that can find the maximum correlation filter functions automatically from a given set of patterns of interest. This filter system also uses a kind of maximum separation principle so that the resulting feature vectors can be easily used by classifiers. We demonstrate how such a filter system stabilizes in states that correspond to the theoretically derived filter functions and how this filter system reacts to invariance properties in the trainings set. | |||||
BibTeX:
@article{Lenz1991d,
author = {Lenz, Reiner},
title = {On probabilistic invariance},
journal = {Neural Networks},
year = {1991},
volume = {4},
number = {5},
pages = {627--641},
url = {http://www.sciencedirect.com/science/article/B6T08-485RHJV-29/2/db2d62a1a9b6015b0f9ff469350c8552}
}
|
|||||
| Magnusson, M., Lenz, R. & Danielsson, P.-E. | Evaluation of methods for shaded surface display of CT-volumes [BibTeX] |
1991 | Computerized Medical Imaging and Graphics Vol. 15(4), pp. 247-256 |
article | |
BibTeX:
@article{Magnusson1991,
author = {Maria Magnusson and Reiner Lenz and Per-Erik Danielsson},
title = {Evaluation of methods for shaded surface display of CT-volumes},
journal = {Computerized Medical Imaging and Graphics},
year = {1991},
volume = {15},
number = {4},
pages = {247-256}
}
|
|||||
| Österberg, M. & Lenz, R. | Learning Filter Systems: Recent Developments and New Experiments [BibTeX] |
1991 | Proc. Swedish Society for Automated Image Analysis Symposium, Stockholm, Sweden |
inproceedings | |
BibTeX:
@inproceedings{Osterberg1991,
author = {Mats Österberg and Reiner Lenz},
title = {Learning Filter Systems: Recent Developments and New Experiments},
booktitle = {Proc. Swedish Society for Automated Image Analysis Symposium, Stockholm, |
|||||
| Österberg, M. & Lenz, R. | Learning Filter Systems: Basic principles and some applications [BibTeX] |
1991 | 7th Scandinavian Conference on Image Analysis | inproceedings | |
BibTeX:
@inproceedings{Osterberg1991a,
author = {Mats Österberg and Reiner Lenz},
title = {Learning Filter Systems: Basic principles and some applications},
booktitle = {7th Scandinavian Conference on Image Analysis},
year = {1991}
}
|
|||||
| Seger, O. & Lenz, R. | Modelling a confocal microscope with operator methods [BibTeX] |
1991 | Proc. Swedish Society for Automated Image Analysis Symposium, Stockholm, Sweden |
inproceedings | |
BibTeX:
@inproceedings{Seger1991,
author = {Olle Seger and Reiner Lenz},
title = {Modelling a confocal microscope with operator methods},
booktitle = {Proc. Swedish Society for Automated Image Analysis Symposium, Stockholm, |
|||||
| Lenz, R. | A Group Theoretical Investigation of Motion [BibTeX] |
1990 | Proc. Swedish Society for Automated Image Analysis Symposium, Linköping, Sweden |
inproceedings | |
BibTeX:
@inproceedings{Lenz1990,
author = {Reiner Lenz},
title = {A Group Theoretical Investigation of Motion},
booktitle = {Proc. Swedish Society for Automated Image Analysis Symposium, Linköping, |
|||||
| Lenz, R. & Österberg, M. | Learning Filter Systems [BibTeX] |
1990 | Proc. Swedish Society for Automated Image Analysis Symposium, Linköping, Sweden |
inproceedings | |
BibTeX:
@inproceedings{Lenz1990a,
author = {Reiner Lenz and Mats Österberg},
title = {Learning Filter Systems},
booktitle = {Proc. Swedish Society for Automated Image Analysis Symposium, Linköping, |
|||||
| Lenz, R. & Österberg, M. | Learning Filter Systems [BibTeX] |
1990 | Proc. Int. Neural Networks Conference, Paris | inproceedings | |
BibTeX:
@inproceedings{Lenz1990b,
author = {Reiner Lenz and Mats Österberg},
title = {Learning Filter Systems},
booktitle = {Proc. Int. Neural Networks Conference, Paris},
year = {1990}
}
|
|||||
| Lenz, R. & Seger, O. | A review of operator methods in fourier optics [BibTeX] |
1990 | Proc. Micro 90; Transactions of the Royal Microscopical Scociety, pp. 243-246 | inproceedings | |
BibTeX:
@inproceedings{Lenz1990c,
author = {Reiner Lenz and Olle Seger},
title = {A review of operator methods in fourier optics},
booktitle = {Proc. Micro 90; Transactions of the Royal Microscopical Scociety},
publisher = {A. Hilger},
year = {1990},
pages = {243--246}
}
|
|||||
| Lenz, R. & Österberg, M. | Learning Filter Systems [BibTeX] |
1990 | Proc. Int. Joint Conference on Neural Networks, San Diego | inproceedings | |
BibTeX:
@inproceedings{Lenz1990d,
author = {Reiner Lenz and Mats Österberg},
title = {Learning Filter Systems},
booktitle = {Proc. Int. Joint Conference on Neural Networks, San Diego},
year = {1990}
}
|
|||||
| Lenz, R. | Group Theoretical Methods in Image Processing [BibTeX] |
1990 | book | ||
BibTeX:
@book{Lenz1990e,
author = {R. Lenz},
title = {Group Theoretical Methods in Image Processing},
publisher = {Springer Verlag},
year = {1990}
}
|
|||||
| Lenz, R. | Group invariant pattern recognition | 1990 | Pattern Recognition Vol. 23(1-2), pp. 199-217 |
article | URL |
| Abstract: In this paper we develop a group theoretical model for the feature extraction part of pattern recognition systems. We argue that the features used should reflect the regularities in the environment in which the system exists. We develop first a group theoretical model to describe these regularities, and then we show how to construct a feature extraction system that reflects these regularities. We show why the so found filter functions often appear as solutions to optimality problems and why they often have some nice properties such as invariance under Fourier transformation. We will mainly investigate problems connected to the group of rotations (in 2-D and 3-D space) but we will touch other types of symmetries as well. | |||||
BibTeX:
@article{Lenz1990f,
author = {Lenz, Reiner},
title = {Group invariant pattern recognition},
journal = {Pattern Recognition},
year = {1990},
volume = {23},
number = {1-2},
pages = {199--217},
url = {http://www.sciencedirect.com/science/article/B6V14-48MPJMT-K2/2/845c1457606b0f7db207150898da031e}
}
|
|||||
| Grönqvist, A. & Lenz, R. | Detection of Blood Vessels in 3-D MR-Images [BibTeX] |
1989 | Proc. of the Swedish Society for Automated Image Analysis Symposium, Gothenburg, Sweden |
inproceedings | |
BibTeX:
@inproceedings{Gronqvist1989,
author = {Anders Grönqvist and Reiner Lenz},
title = {Detection of Blood Vessels in 3-D MR-Images},
booktitle = {Proc. of the Swedish Society for Automated Image Analysis Symposium, |
|||||
| Grönqvist, A. & Lenz, R. | Detection of Blood Vessels in 3-D MR-Images [BibTeX] |
1989 | Proc. of the 1989 IEEE/INNS International Joint Conference on Neural Nets |
inproceedings | |
BibTeX:
@inproceedings{Gronqvist1989a,
author = {Anders Grönqvist and Reiner Lenz},
title = {Detection of Blood Vessels in 3-D MR-Images},
booktitle = {Proc. of the 1989 IEEE/INNS International Joint Conference on Neural |
|||||
| Lenz, R. & Österberg, M. | Adaptive, Invariant Filter Systems [BibTeX] |
1989 | Proc. of the Swedish Society for Automated Image Analysis Symposium, Gothenburg, Sweden |
inproceedings | |
BibTeX:
@inproceedings{Lenz1989,
author = {Reiner Lenz and Mats Österberg},
title = {Adaptive, Invariant Filter Systems},
booktitle = {Proc. of the Swedish Society for Automated Image Analysis Symposium, |
|||||
| Lenz, R. | A Group Theoretical Approach to Filter Design [BibTeX] |
1989 | Proc. Int. Conf. Accoustics, Speech and Sig. Proc. | inproceedings | |
BibTeX:
@inproceedings{Lenz1989a,
author = {Reiner Lenz},
title = {A Group Theoretical Approach to Filter Design},
booktitle = {Proc. Int. Conf. Accoustics, Speech and Sig. Proc.},
year = {1989}
}
|
|||||
| Lenz, R. | Describing and recognizing group-invariant pattern classes with group-sampling | 1989 | Pattern Recognition Letters Vol. 9(3), pp. 169-173 |
article | URL |
| Abstract: In this paper we investigate how a pattern recognition system can describe a whole class of patterns and how it can extract these patterns from an unknown image. We assume that the pattern class is defined in terms of a group operation and a prototype pattern. We will then construct a class of symbols that describe such a class uniquely. Finally we discuss the problem how to decide if a given, unknown gray value pattern was a member of a given pattern class or not. We will mainly discuss the problem in the case where the group defining the pattern class is a rotation group (in two or three dimensions) but we will mention results for other interesting groups as well. | |||||
BibTeX:
@article{Lenz1989b,
author = {Lenz, Reiner},
title = {Describing and recognizing group-invariant pattern classes with group-sampling},
journal = {Pattern Recognition Letters},
year = {1989},
volume = {9},
number = {3},
pages = {169--173},
url = {http://www.sciencedirect.com/science/article/B6V15-48MXRX6-8V/2/4bf44b2cefa566b16b3f8c6d1b1bc210}
}
|
|||||
| Lenz, R. | Group-theoretical model of feature extraction | 1989 | Journal of the Optical Society of America A (Optics and Image Science) Vol. 6(6)J. Opt. Soc. Am. A, Opt. Image Sci. (USA), pp. 827-34 |
article | |
| Abstract: A group-theoretically motivated investigation of feature extraction is described. A feature extraction unit is defined as a complex-valued function on a signal space. It is assumed that the signal space possesses a group-theoretically defined regularity that the authors introduce. First the concept of a symmetrical signal space is derived. Feature mappings then are introduced on signal spaces and some properties of feature mappings on symmetrical signal spaces are investigated. Next the investigation is restricted to linear features, and an overview of all possible linear features is given. Also it is shown how a set of linear features can be used to construct a nonlinear feature that has the same value for all patterns in a class of similar patterns. These results are used to construct filter functions that can be used to detect patterns in two- and three-dimensional images independent of the orientation of the pattern in the image. Finally it is sketched briefly how the theory developed here can be applied to solve other, symmetrical problems in imaging processing | |||||
BibTeX:
@article{Lenz1989c,
author = {Lenz, R.},
title = {Group-theoretical model of feature extraction},
booktitle = {J. Opt. Soc. Am. A, Opt. Image Sci. (USA)},
journal = {Journal of the Optical Society of America A (Optics and Image Science)},
year = {1989},
volume = {6},
number = {6},
pages = {827--34}
}
|
|||||
| Lenz, R. | A group theoretical approach to filter design [BibTeX] |
1988 | Proc. of the Swedish Society for Automated Image Analysis Symposium, Lund, Sweden |
inproceedings | |
BibTeX:
@inproceedings{Lenz1988,
author = {Reiner Lenz},
title = {A group theoretical approach to filter design},
booktitle = {Proc. of the Swedish Society for Automated Image Analysis Symposium, |
|||||
| Magnusson, M., Lenz, R. & Danielsson, P.-E. | A comparison of some shaded surface display methods [BibTeX] |
1988 | Proc. of the Swedish Society for Automated Image Analysis Symposium, Lund, Sweden |
inproceedings | |
BibTeX:
@inproceedings{Magnusson1988,
author = {Maria Magnusson and Reiner Lenz and Per-Erik Danielsson},
title = {A comparison of some shaded surface display methods},
booktitle = {Proc. of the Swedish Society for Automated Image Analysis Symposium, |
|||||
| Magnusson, M., Lenz, R. & Danielsson, P.-E. | Evaluation of methods for shaded surface display of CT-volumes | 1988 | 9th International Conference on Pattern Recognition (IEEE Cat. No.88CH2614-6), pp. 1287-94 | inproceedings | |
| Abstract: Twelve methods are evaluated to analyze an ideal sphere and a real human skull. They are different combinations of principles for detection of the surface to be displayed (gray-value threshold, gradient threshold, and zero-crossing of the second derivative), localizing this surface in space (including both grid-point accuracy and subvoxel accuracy), and finally estimating the direction of the surface normal (from the gradient in the 2-D depth image and from the gradient in the 3-D volume). The best quality is obtained by zero-crossing detection, subvoxel localization, and 3-D gradient orientation | |||||
BibTeX:
@inproceedings{Magnusson1988a,
author = {Magnusson, M. and Lenz, R. and Danielsson, P.-E.},
title = {Evaluation of methods for shaded surface display of CT-volumes},
booktitle = {9th International Conference on Pattern Recognition (IEEE Cat. No.88CH2614-6)},
publisher = {IEEE Comput. Soc. Press},
year = {1988},
pages = {1287--94}
}
|
|||||
| Lenz, R. & Gudmundsson, B. | 3-D Image Processing and Display - A Survey [BibTeX] |
1987 | ACTA Stereologica Vol. 6, Suppl. I, pp. 137-142 |
article | |
BibTeX:
@article{Lenz1987,
author = {R. Lenz and Björn Gudmundsson},
title = {3-D Image Processing and Display - A Survey},
journal = {ACTA Stereologica},
year = {1987},
volume = {6, Suppl. I},
pages = {137-142}
}
|
|||||
| Lenz, R. | Optimal filters for the detection of linear patterns in 2-D and higher dimensional images | 1987 | Pattern Recognition Vol. 20(2), pp. 163-172 |
article | URL |
| Abstract: It is shown that the rotation-invariant operators form a set of orthogonal basis functions which is optimal for a wide range of 2-D and 3-D feature-detection operations. The optimality criterion used is based on the Karhunen-Loeve expansion of the local image data. This is a generalization of the work of Zucker and Hummel who showed that these filters are optimal filters for the detection of step edges in 2-D and 3-D images. | |||||
BibTeX:
@article{Lenz1987a,
author = {Lenz, Reiner},
title = {Optimal filters for the detection of linear patterns in 2-D and higher dimensional images},
journal = {Pattern Recognition},
year = {1987},
volume = {20},
number = {2},
pages = {163--172},
url = {http://www.sciencedirect.com/science/article/B6V14-48MPKNV-V5/2/7956336f8b2d6cc19d25bd79b0f03ee5}
}
|
|||||
| Lenz, R. | Rotation-invariant operators and scale-space filtering | 1987 | Pattern Recognition Letters Vol. 6(3), pp. 151-154 |
article | URL |
| Abstract: We analyse the `Laplacian of the Gaussian' approach with the help of rotation-invariant operators and we show how the original image is related to the Gaussian (and Laplace-) filtered version of it. | |||||
BibTeX:
@article{Lenz1987b,
author = {Lenz, Reiner},
title = {Rotation-invariant operators and scale-space filtering},
journal = {Pattern Recognition Letters},
year = {1987},
volume = {6},
number = {3},
pages = {151--154},
url = {http://www.sciencedirect.com/science/article/B6V15-48MXRGH-45/2/01c68de7cf9516ba6403b93dcca787c0}
}
|
|||||
| Lenz, R. | Reconstruction, Processing and Display of 3D-Images [BibTeX] |
1986 | School: Linköping University, Sweden | phdthesis | |
BibTeX:
@phdthesis{Lenz1986,
author = {Reiner Lenz},
title = {Reconstruction, Processing and Display of 3D-Images},
school = {Linköping University, Sweden},
year = {1986}
}
|
|||||
| Lenz, R. | Experiments in 3-D Image Processing [BibTeX] |
1986 | Proc. of the Swedish Society for Automated Image Analysis Symposium, Uppsala, Sweden |
inproceedings | |
BibTeX:
@inproceedings{Lenz1986a,
author = {Reiner Lenz},
title = {Experiments in 3-D Image Processing},
booktitle = {Proc. of the Swedish Society for Automated Image Analysis Symposium, |
|||||
| Lenz, R. | 3-D Reconstruction with a Projection onto Convex Sets Algorithm [BibTeX] |
1986 | Optics Communications Vol. 57(1), pp. . |
article | |
BibTeX:
@article{Lenz1986b,
author = {R. Lenz},
title = {3-D Reconstruction with a Projection onto Convex Sets Algorithm},
journal = {Optics Communications},
year = {1986},
volume = {57},
number = {1},
pages = {.}
}
|
|||||
| Lenz, R., Gudmundsson, B., Lindskog, B. & Danielsson, P.E. | Display of Density Volumes [BibTeX] |
1986 | IEEE Computer Graphics and Applications Vol. 6(7), pp. 20-29 |
article | |
BibTeX:
@article{Lenz1986c,
author = {R. Lenz and B. Gudmundsson and B. Lindskog and P. E. Danielsson},
title = {Display of Density Volumes},
journal = {IEEE Computer Graphics and Applications},
year = {1986},
volume = {6},
number = {7},
pages = {20-29}
}
|
|||||
| Lenz, R., Gudmundsson, B. & Lindskog, B. | Manipulation and display of 3-D images for surgical planning | 1986 | Vol. 593Proc. SPIE - Int. Soc. Opt. Eng. (USA), pp. 96-102 |
inproceedings | |
| Abstract: The authors describe some experiments in the processing and display of 3-D images from CT-scanners. In the first part they describe the implemented surface displays and in the second part they discuss some applications of 3-D image transformations | |||||
BibTeX:
@inproceedings{Lenz1986d,
author = {Lenz, R. and Gudmundsson, B. and Lindskog, B.},
title = {Manipulation and display of 3-D images for surgical planning},
booktitle = {Proc. SPIE - Int. Soc. Opt. Eng. (USA)},
year = {1986},
volume = {593},
pages = {96--102}
}
|
|||||
| Lenz, R. | 3-D reconstruction with a projection onto convex sets algorithm | 1986 | Optics Communications Vol. 57(1)Opt. Commun. (Netherlands), pp. 21-5 |
article | |
| Abstract: A reconstruction scheme based on linear systems theory is described which improves the resolution of 3-D light microscopic images along the optical axis. The method iteratively eliminates the contributions from the out-of-focus planes. It converges to the true solution in the absence of noise | |||||
BibTeX:
@article{Lenz1986e,
author = {Lenz, R.},
title = {3-D reconstruction with a projection onto convex sets algorithm},
booktitle = {Opt. Commun. (Netherlands)},
journal = {Optics Communications},
year = {1986},
volume = {57},
number = {1},
pages = {21--5}
}
|
|||||
| Lenz, R. | Rotation-invariant operators for 2D and higher dimensional images | 1986 | Advances in Image Processing and Pattern Recognition. Proceedings of the International Conference, pp. 164-8 | inproceedings | |
| Abstract: The idea of detecting edges in digital images by fitting a surface to a neighborhood of each image point, introduced by Prewitt (1979), was modified by Hummel (1979), who selected the type of surfaces depending on the type of the interesting target patterns. His method thus consists of two steps: selecting the class of surfaces such that they fit the target patterns best in a mean square sense, and finding the surface in the selected class which approximates the image data best and deciding whether this surface fits the image data well enough. Results obtained are generalized in several ways. First it is proven that the rotation-invariant operators are optimal basis functions for a large class of features and it is shown how the weight function h(r) can be computed from the given features of interest. Secondly, the results are generalized to images of arbitrary dimension (two or more) | |||||
BibTeX:
@inproceedings{Lenz1986f,
author = {Lenz, R.},
title = {Rotation-invariant operators for 2D and higher dimensional images},
booktitle = {Advances in Image Processing and Pattern Recognition. Proceedings of the International Conference},
publisher = {North-Holland},
year = {1986},
pages = {164--8}
}
|
|||||
| Lenz, R. | Rotation-invariant operators | 1986 | Eighth International Conference on Pattern Recognition. Proceedings (Cat. No.86CH2342-4), pp. 1130-2 | inproceedings | |
| Abstract: Rotation-invariant operators are described that are filters of the form f(x,y)=f(r,φ)=hn(r)exp(inφ) in the two dimensional case and f(X)=f(rU)=hn(r)Sn(U) in the higher-dimensional cases. Their usefulness is demonstrated for a large number of pattern recognition purposes, including edge and line detection. Some properties of these filters that make them a natural choice for the class of problems considered are summarized. It is shown how the weight functions hn can be constructed to make the resulting filters optimal in a certain sense. Some other applications where this type of function is useful are mentioned | |||||
BibTeX:
@inproceedings{Lenz1986g,
author = {Lenz, R.},
title = {Rotation-invariant operators},
booktitle = {Eighth International Conference on Pattern Recognition. Proceedings (Cat. No.86CH2342-4)},
publisher = {IEEE Comput. Soc. Press},
year = {1986},
pages = {1130--2}
}
|
|||||
| Carlsson, K., Liljeborg, A., Majlöf, L., N.Åslund, Danielsson, P.E. & Lenz, R. | Three-dimensional Microscopy using a Confocal Laser Scanning Microscope [BibTeX] |
1985 | Optics Letters Vol. 10, pp. 53-55 |
article | |
BibTeX:
@article{Carlsson1985,
author = {K. Carlsson and A. Liljeborg and L. Majlöf and N.Åslund and P. E. Danielsson and R. Lenz},
title = {Three-dimensional Microscopy using a Confocal Laser Scanning Microscope},
journal = {Optics Letters},
year = {1985},
volume = {10},
pages = {53-55}
}
|
|||||
| Lenz, R. | 3-D Filters for Noise Reduction and 3-D Display [BibTeX] |
1985 | Proc. of the Swedish Society for Automated Image Analysis Symposium, Stockholm, Sweden |
inproceedings | |
BibTeX:
@inproceedings{Lenz1985,
author = {Reiner Lenz},
title = {3-D Filters for Noise Reduction and 3-D Display},
booktitle = {Proc. of the Swedish Society for Automated Image Analysis Symposium, |
|||||
| Lenz, R., Danielsson, P.-E. & Cronström, S. | Application of 3-D Thinning and Filtering in the Display of 3-D Images [BibTeX] |
1985 | Proc. of the 4th Scandinavian Conference on Image Analysis, Trondheim, Norway |
inproceedings | |
BibTeX:
@inproceedings{Lenz1985a,
author = {Reiner Lenz and Per-Erik Danielsson and Staffan Cronström},
title = {Application of 3-D Thinning and Filtering in the Display of 3-D |
|||||
| Lenz, R., Danielsson, P.-E., Gudmundsson, B. & Edholm, P. | Experiments in Processing and Display of 3D Radiography Images [BibTeX] |
1985 | Proc. XIV ICMBE and VII ICMP, Espoo, Finland | inproceedings | |
BibTeX:
@inproceedings{Lenz1985b,
author = {Reiner Lenz and Per-Erik Danielsson and Björn Gudmundsson and Paul |
|||||
| Lenz, R. | Processing and Presentation of 3D-images [BibTeX] |
1984 | Proc. of the International Symposium on Medical Images and Icons, Arlington, Virginia, USA |
inproceedings | |
BibTeX:
@inproceedings{Lenz1984,
author = {Reiner Lenz},
title = {Processing and Presentation of 3D-images},
booktitle = {Proc. of the International Symposium on Medical Images and Icons, |
|||||
| Lenz, R. | Processing and Presentation of 3-D volumes [BibTeX] |
1984 | Proc. of the Swedish Society for Automated Image Analysis Symposium, Linköping |
inproceedings | |
BibTeX:
@inproceedings{Lenz1984a,
author = {Reiner Lenz},
title = {Processing and Presentation of 3-D volumes},
booktitle = {Proc. of the Swedish Society for Automated Image Analysis Symposium, |
|||||
| Lenz, R., Danielsson, P.-E., Cronström, S. & Gudmundsson, B. | Presentation and Perception of 3D-images [BibTeX] |
1984 | NATO-ASI, Pictorial Information Systems in Medicine, Braunlage, West-Germany | inproceedings | |
BibTeX:
@inproceedings{Lenz1984b,
author = {Reiner Lenz and Per-Erik Danielsson and Staffan Cronström and Björn |
|||||
| Lenz, R., Danielsson, P.-E. & Gudmundsson, B. | Interactive display of 3D-images in PICAP II | 1984 | Vol. 507Proc. SPIE - Int. Soc. Opt. Eng. (USA), pp. 19-24 |
inproceedings | |
| Abstract: The authors present some experiments in processing and display of true 3D-images (density volumes). The experiments have been carried out on the PICAP II image processing system | |||||
BibTeX:
@inproceedings{Lenz1984c,
author = {Lenz, R. and Danielsson, P.-E. and Gudmundsson, B.},
title = {Interactive display of 3D-images in PICAP II},
booktitle = {Proc. SPIE - Int. Soc. Opt. Eng. (USA)},
year = {1984},
volume = {507},
pages = {19--24}
}
|
|||||
| Lenz, R., Danielsson, P.-E., Crontstrom, S., Gudmundsson, B. & Edholm, P. | Presentation and perception of 3D-images | 1984 | Seventh International Conference on Pattern Recognition (Cat. No. 84CH2046-1), pp. 749-51 | inproceedings | |
| Abstract: Several methods for display of 3-D data are presented. Basic representations such as look-through projections and surface display are combined with stereo effects and interactively controlled motion to give a better 3-D impressions. The effects of various preprocessing steps are discussed | |||||
BibTeX:
@inproceedings{Lenz1984d,
author = {Lenz, R. and Danielsson, P.-E. and Crontstrom, S. and Gudmundsson, B. and Edholm, P.},
title = {Presentation and perception of 3D-images},
booktitle = {Seventh International Conference on Pattern Recognition (Cat. No. 84CH2046-1)},
publisher = {IEEE Comput. Soc. Press},
year = {1984},
pages = {749--51}
}
|
|||||
| Reinhardt, E., Lenz, R., Greiner, W. & Schenk, U. | Diagnostic Relevance of Visually non Suspect Cells for Cancer Diagnosis [BibTeX] |
1982 | Int. Conf. High Resolution Cell Image Analysis, Los Angeles | inproceedings | |
BibTeX:
@inproceedings{Reinhardt1982,
author = {E.R. Reinhardt and R. Lenz and W. Greiner and U. Schenk},
title = {Diagnostic Relevance of Visually non Suspect Cells for Cancer Diagnosis},
booktitle = {Int. Conf. High Resolution Cell Image Analysis, Los Angeles},
year = {1982}
}
|
|||||
| Reinhardt, E., Schwarzmann, P. & Lenz, R. | Satellite Image Analysis [BibTeX] |
1982 | Solar Radiation Data Series F, Vol. 2, pp. 288 - 292 | inproceedings | |
BibTeX:
@inproceedings{Reinhardt1982a,
author = {E.R. Reinhardt and P. Schwarzmann and R. Lenz},
title = {Satellite Image Analysis},
booktitle = {Solar Radiation Data Series F, Vol. 2},
year = {1982},
pages = {288 - 292}
}
|
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| Reinhardt, E., Blanz, W., Erhardt, R., Greiner, W., Hornstein, B., Kringler, W., Lenz, R., Schimpf, I., Schlipf, W., Schwarzmann, P., Strassle, G. & Bloss, W. | Automated classification of cytological specimen based on multistage pattern recognition | 1982 | Proceedings of the 6th International Conference on Pattern Recognition, pp. 153-9 | inproceedings | |
| Abstract: A prescreening system for the early detection of uterine cancer was developed. For the diagnosis of each input specimen (PAP-stained), a figure of malignancy has to be calculated automatically. Methods, problems and results of the whole project are summarized in this paper. Some thousand microscopic subfields of a specimen are successively scanned by an optimized TV-camera with high spatial resolution. The automated specimen analysis can be described by a two step procedure: single cell classification and evaluation of cell population. For the single cell classifier only features derived from the nuclear images are used. The pattern recognition procedures are based on a processor-oriented strategy, and can be adapted to other cytological specimen. The algorithms have been tested with 3.105 cell images of about 300 specimens | |||||
BibTeX:
@inproceedings{Reinhardt1982b,
author = {Reinhardt, E.R. and Blanz, W.E. and Erhardt, R. and Greiner, W. and Hornstein, B. and Kringler, W. and Lenz, R. and Schimpf, I. and Schlipf, W. and Schwarzmann, P. and Strassle, G. and Bloss, W.H.},
title = {Automated classification of cytological specimen based on multistage pattern recognition},
booktitle = {Proceedings of the 6th International Conference on Pattern Recognition},
publisher = {IEEE},
year = {1982},
pages = {153--9}
}
|
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| Blanz, W., Lenz, R. & Reinhardt, E. | Allgemeiner Ansatz zur Bildsegmentation [BibTeX] |
1981 | DFG-Schwerpunktprogram Digitale Signalverarbeitung. Göttingen | inproceedings | |
BibTeX:
@inproceedings{Blanz1981,
author = {W.E. Blanz and R.L. Lenz and E.R. Reinhardt},
title = {Allgemeiner Ansatz zur Bildsegmentation},
booktitle = {DFG-Schwerpunktprogram Digitale Signalverarbeitung. Göttingen},
year = {1981}
}
|
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| Reinhardt, E., Laub, G. & Lenz, R. | Rekonstruktion von Schichtbildern mit Hilfe inkohärent-optischer Abbildungssysteme [BibTeX] |
1980 | Tagung Erzeugung und Analyse von Bildern und Strukturen | inproceedings | |
BibTeX:
@inproceedings{Reinhardt1980,
author = {E.R. Reinhardt and G. Laub and R. Lenz},
title = {Rekonstruktion von Schichtbildern mit Hilfe inkohärent-optischer |
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