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Author (up) Javier Varona; Antoni Jaume-i-Capo; Jordi Gonzalez; Francisco Jose Perales
Title Toward Natural Interaction through Visual Recognition of Body Gestures in Real-Time Type Journal
Year 2008 Publication Interacting with Computers, diu 10,1016/j.intcom.2008.10.001, available on line Abbreviated Journal
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Call Number ISE @ ise @ VJG2008 Serial 1022
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Author (up) Javier Varona; Jordi Gonzalez; Ignasi Rius; Juan J. Villanueva
Title Importance of Detection for Video Surveillance Applications Type Journal
Year 2008 Publication Optical Engineering, vol. 47(8), 087201/1–9 Abbreviated Journal
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Call Number ISE @ ise @ VGR2008 Serial 998
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Author (up) Javier Varona; Jordi Gonzalez; Xavier Roca; Juan J. Villanueva
Title iTrack: Image-based Probabilistic Tracking of People. Type Conference Article
Year 2000 Publication 15 th International Conference on Pattern Recognition Abbreviated Journal
Volume 3 Issue Pages 1122-1125
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Address Barcelona.
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Area Expedition Conference ICPR
Notes ISE Approved no
Call Number ISE @ ise @ VGR2000a Serial 228
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Author (up) Javier Varona; Jordi Gonzalez; Xavier Roca; Juan J. Villanueva
Title Automatic Selection of Keyframes for Activity Recognition. Type Miscellaneous
Year 2000 Publication International Workshop on Articulated Motion and Deformable Objects ( AMDO&rsquo), 173–181. Abbreviated Journal
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Address Palma de Mallorca.
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Notes ISE Approved no
Call Number ISE @ ise @ VGR2000b Serial 243
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Author (up) Javier Varona; Jordi Gonzalez; Xavier Roca; Juan J. Villanueva
Title Appearance Tracking for Video Surveillance Type Miscellaneous
Year 2003 Publication Abbreviated Journal
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Notes ISE Approved no
Call Number ISE @ ise @ VGR2003a Serial 358
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Author (up) Javier Varona; Jordi Gonzalez; Xavier Roca; Juan J. Villanueva
Title Appearance Tracking for Video Surveillance Type Miscellaneous
Year 2003 Publication In Pattern Recognition and Image Analysis, Lecture Notes in Computer Science 2652:1041–1048 Abbreviated Journal
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Address Springer-Verlag
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Notes ISE Approved no
Call Number ISE @ ise @ VGR2003b Serial 425
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Author (up) Javier Varona; Juan J. Villanueva
Title Neural Networks for Early Vision. Type Miscellaneous
Year 1997 Publication Proceedings of the VII NSPRIA, Vol. I. Abbreviated Journal
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Address CVC (UAB)
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Notes Approved no
Call Number ISE @ ise @ VaV1997b Serial 62
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Author (up) Javier Varona; Juan J. Villanueva
Title Neural networks as spatial filters for image processing: Neurofilters Type Report
Year 1996 Publication Technical Report #07 Abbreviated Journal
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Address CVC (UAB)
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Notes Approved no
Call Number ISE @ ise @ VaV1996 Serial 95
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Author (up) Javier Varona; Juan J. Villanueva
Title NeuroFilters: Neural Networks for image Processing. Type Miscellaneous
Year 1997 Publication Vision Systems: New image Processing Techniques and Applications Algorithms, Methods, and Components. Proceedings of the SPIE. Abbreviated Journal
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Address Munich
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Notes Approved no
Call Number ISE @ ise @ VaV1997a Serial 207
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Author (up) Javier Vazquez
Title Content-based Colour Space Type Report
Year 2007 Publication CVC Technical Report #116 Abbreviated Journal
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Address CVC (UAB)
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Call Number Admin @ si @ Vaz2007b Serial 828
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Author (up) Javier Vazquez
Title Colour Constancy in Natural Through Colour Naming and Sensor Sharpening Type Book Whole
Year 2011 Publication PhD Thesis, Universitat Autonoma de Barcelona-CVC Abbreviated Journal
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Abstract Colour is derived from three physical properties: incident light, object reflectance and sensor sensitivities. Incident light varies under natural conditions; hence, recovering scene illuminant is an important issue in computational colour. One way to deal with this problem under calibrated conditions is by following three steps, 1) building a narrow-band sensor basis to accomplish the diagonal model, 2) building a feasible set of illuminants, and 3) defining criteria to select the best illuminant. In this work we focus on colour constancy for natural images by introducing perceptual criteria in the first and third stages.
To deal with the illuminant selection step, we hypothesise that basic colour categories can be used as anchor categories to recover the best illuminant. These colour names are related to the way that the human visual system has evolved to encode relevant natural colour statistics. Therefore the recovered image provides the best representation of the scene labelled with the basic colour terms. We demonstrate with several experiments how this selection criterion achieves current state-of-art results in computational colour constancy. In addition to this result, we psychophysically prove that usual angular error used in colour constancy does not correlate with human preferences, and we propose a new perceptual colour constancy evaluation.
The implementation of this selection criterion strongly relies on the use of a diagonal
model for illuminant change. Consequently, the second contribution focuses on building an appropriate narrow-band sensor basis to represent natural images. We propose to use the spectral sharpening technique to compute a unique narrow-band basis optimised to represent a large set of natural reflectances under natural illuminants and given in the basis of human cones. The proposed sensors allow predicting unique hues and the World colour Survey data independently of the illuminant by using a compact singularity function. Additionally, we studied different families of sharp sensors to minimise different perceptual measures. This study brought us to extend the spherical sampling procedure from 3D to 6D.
Several research lines still remain open. One natural extension would be to measure the
effects of using the computed sharp sensors on the category hypothesis, while another might be to insert spatial contextual information to improve category hypothesis. Finally, much work still needs to be done to explore how individual sensors can be adjusted to the colours in a scene.
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Corporate Author Thesis Ph.D. thesis
Publisher Ediciones Graficas Rey Place of Publication Editor Maria Vanrell;Graham D. Finlayson
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Notes CIC Approved no
Call Number Admin @ si @ Vaz2011a Serial 1785
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Author (up) Javier Vazquez; C. Alejandro Parraga; Maria Vanrell
Title Ordinal pairwise method for natural images comparison Type Journal Article
Year 2009 Publication Perception Abbreviated Journal PER
Volume 38 Issue Pages 180
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Abstract 38(Suppl.)ECVP Abstract Supplement
We developed a new psychophysical method to compare different colour appearance models when applied to natural scenes. The method was as follows: two images (processed by different algorithms) were displayed on a CRT monitor and observers were asked to select the most natural of them. The original images were gathered by means of a calibrated trichromatic digital camera and presented one on top of the other on a calibrated screen. The selection was made by pressing on a 6-button IR box, which allowed observers to consider not only the most natural but to rate their selection. The rating system allowed observers to register how much more natural was their chosen image (eg, much more, definitely more, slightly more), which gave us valuable extra information on the selection process. The results were analysed considering both the selection as a binary choice (using Thurstone's law of comparative judgement) and using Bradley-Terry method for ordinal comparison. Our results show a significant difference in the rating scales obtained. Although this method has been used in colour constancy algorithm comparisons, its uses are much wider, eg to compare algorithms of image compression, rendering, recolouring, etc.
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Notes CIC Approved no
Call Number CAT @ cat @ VPV2009b Serial 1191
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Author (up) Javier Vazquez; C. Alejandro Parraga; Maria Vanrell; Ramon Baldrich
Title Color Constancy Algorithms: Psychophysical Evaluation on a New Dataset Type Journal Article
Year 2009 Publication Journal of Imaging Science and Technology Abbreviated Journal
Volume 53 Issue 3 Pages 031105–9
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Abstract The estimation of the illuminant of a scene from a digital image has been the goal of a large amount of research in computer vision. Color constancy algorithms have dealt with this problem by defining different heuristics to select a unique solution from within the feasible set. The performance of these algorithms has shown that there is still a long way to go to globally solve this problem as a preliminary step in computer vision. In general, performance evaluation has been done by comparing the angular error between the estimated chromaticity and the chromaticity of a canonical illuminant, which is highly dependent on the image dataset. Recently, some workers have used high-level constraints to estimate illuminants; in this case selection is based on increasing the performance on the subsequent steps of the systems. In this paper we propose a new performance measure, the perceptual angular error. It evaluates the performance of a color constancy algorithm according to the perceptual preferences of humans, or naturalness (instead of the actual optimal solution) and is independent of the visual task. We show the results of a new psychophysical experiment comparing solutions from three different color constancy algorithms. Our results show that in more than a half of the judgments the preferred solution is not the one closest to the optimal solution. Our experiments were performed on a new dataset of images acquired with a calibrated camera with an attached neutral grey sphere, which better copes with the illuminant variations of the scene.
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Call Number CAT @ cat @ VPV2009a Serial 1171
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Author (up) Javier Vazquez; G. D. Finlayson; Maria Vanrell
Title A compact singularity function to predict WCS data and unique hues Type Conference Article
Year 2010 Publication 5th European Conference on Colour in Graphics, Imaging and Vision and 12th International Symposium on Multispectral Colour Science Abbreviated Journal
Volume Issue Pages 33–38
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Abstract Understanding how colour is used by the human vision system is a widely studied research field. The field, though quite advanced, still faces important unanswered questions. One of them is the explanation of the unique hues and the assignment of color names. This problem addresses the fact of different perceptual status for different colors.
Recently, Philipona and O'Regan have proposed a biological model that allows to extract the reflection properties of any surface independently of the lighting conditions. These invariant properties are the basis to compute a singularity index that predicts the asymmetries presented in unique hues and basic color categories psychophysical data, therefore is giving a further step in their explanation.

In this paper we build on their formulation and propose a new singularity index. This new formulation equally accounts for the location of the 4 peaks of the World colour survey and has two main advantages. First, it is a simple elegant numerical measure (the Philipona measurement is a rather cumbersome formula). Second, we develop a colour-based explanation for the measure.
Address Joensuu, Finland
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ISSN ISBN 9781617388897 Medium
Area Expedition Conference CGIV/MCS
Notes CIC Approved no
Call Number CAT @ cat @ VFV2010 Serial 1324
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Author (up) Javier Vazquez; Graham D. Finlayson; Luis Herranz
Title Improving the perception of low-light enhanced images Type Journal Article
Year 2024 Publication Optics Express Abbreviated Journal
Volume 32 Issue 4 Pages 5174-5190
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Abstract Improving images captured under low-light conditions has become an important topic in computational color imaging, as it has a wide range of applications. Most current methods are either based on handcrafted features or on end-to-end training of deep neural networks that mostly focus on minimizing some distortion metric —such as PSNR or SSIM— on a set of training images. However, the minimization of distortion metrics does not mean that the results are optimal in terms of perception (i.e. perceptual quality). As an example, the perception-distortion trade-off states that, close to the optimal results, improving distortion results in worsening perception. This means that current low-light image enhancement methods —that focus on distortion minimization— cannot be optimal in the sense of obtaining a good image in terms of perception errors. In this paper, we propose a post-processing approach in which, given the original low-light image and the result of a specific method, we are able to obtain a result that resembles as much as possible that of the original method, but, at the same time, giving an improvement in the perception of the final image. More in detail, our method follows the hypothesis that in order to minimally modify the perception of an input image, any modification should be a combination of a local change in the shading across a scene and a global change in illumination color. We demonstrate the ability of our method quantitatively using perceptual blind image metrics such as BRISQUE, NIQE, or UNIQUE, and through user preference tests.
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Notes MACO Approved no
Call Number Admin @ si @ VFH2024 Serial 4018
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