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| Author | Maria Vanrell; Jordi Vitria; Xavier Roca |
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| Title | A multidimensional scaling approach to explore the behavior of a texture perception algorithm. | Type | Journal Article | |||
| Year | 1997 | Publication | Machine Vision and Applications | Abbreviated Journal | ||
| Volume | 9 | Issue | Pages  |
262–271 | ||
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| Notes | OR;ISE;CIC;MV | Approved | no | |||
| Call Number | BCNPCL @ bcnpcl @ VVR1997 | Serial | 35 | |||
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| Author | Jaime Moreno; Xavier Otazu; Maria Vanrell |
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| Title | Local Perceptual Weighting in JPEG2000 for Color Images | 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 |
255–260 | |||
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| Abstract | The aim of this work is to explain how to apply perceptual concepts to define a perceptual pre-quantizer and to improve JPEG2000 compressor. The approach consists in quantizing wavelet transform coefficients using some of the human visual system behavior properties. Noise is fatal to image compression performance, because it can be both annoying for the observer and consumes excessive bandwidth when the imagery is transmitted. Perceptual pre-quantization reduces unperceivable details and thus improve both visual impression and transmission properties. The comparison between JPEG2000 without and with perceptual pre-quantization shows that the latter is not favorable in PSNR, but the recovered image is more compressed at the same or even better visual quality measured with a weighted PSNR. Perceptual criteria were taken from the CIWaM (Chromatic Induction Wavelet Model). | |||||
| Address | Joensuu, Finland | |||||
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| ISSN | ISBN | 9781617388897 | Medium | |||
| Area | Expedition | Conference | CGIV/MCS | |||
| Notes | CIC | Approved | no | |||
| Call Number | CAT @ cat @ MOV2010a | Serial | 1307 | |||
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| Author | Ivet Rafegas; Maria Vanrell |
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| Title | Color spaces emerging from deep convolutional networks | Type | Conference Article | |||
| Year | 2016 | Publication | 24th Color and Imaging Conference | Abbreviated Journal | ||
| Volume | Issue | Pages |
225-230 | |||
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| Abstract | Award for the best interactive session
Defining color spaces that provide a good encoding of spatio-chromatic properties of color surfaces is an open problem in color science [8, 22]. Related to this, in computer vision the fusion of color with local image features has been studied and evaluated [16]. In human vision research, the cells which are selective to specific color hues along the visual pathway are also a focus of attention [7, 14]. In line with these research aims, in this paper we study how color is encoded in a deep Convolutional Neural Network (CNN) that has been trained on more than one million natural images for object recognition. These convolutional nets achieve impressive performance in computer vision, and rival the representations in human brain. In this paper we explore how color is represented in a CNN architecture that can give some intuition about efficient spatio-chromatic representations. In convolutional layers the activation of a neuron is related to a spatial filter, that combines spatio-chromatic representations. We use an inverted version of it to explore the properties. Using a series of unsupervised methods we classify different type of neurons depending on the color axes they define and we propose an index of color-selectivity of a neuron. We estimate the main color axes that emerge from this trained net and we prove that colorselectivity of neurons decreases from early to deeper layers. |
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| Address | San Diego; USA; November 2016 | |||||
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| Area | Expedition | Conference | CIC | |||
| Notes | CIC | Approved | no | |||
| Call Number | Admin @ si @ RaV2016a | Serial | 2894 | |||
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| Author | C. Alejandro Parraga; Robert Benavente; Maria Vanrell; Ramon Baldrich |
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| Title | Modelling Inter-Colour Regions of Colour Naming Space | Type | Conference Article | |||
| Year | 2008 | Publication | 4th European Conference on Colour in Graphics, Imaging and Vision Proceedings | Abbreviated Journal | ||
| Volume | Issue | Pages |
218–222 | |||
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| Address | Terrassa (Spain) | |||||
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| Area | Expedition | Conference | CGIV08 | |||
| Notes | CAT;CIC | Approved | no | |||
| Call Number | CAT @ cat @ PBV2008 | Serial | 969 | |||
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| Author | Jordi Roca; C. Alejandro Parraga; Maria Vanrell |
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| Title | Categorical Focal Colours are Structurally Invariant Under Illuminant Changes | Type | Conference Article | |||
| Year | 2011 | Publication | European Conference on Visual Perception | Abbreviated Journal | ||
| Volume | Issue | Pages |
196 | |||
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| Abstract | The visual system perceives the colour of surfaces approximately constant under changes of illumination. In this work, we investigate how stable is the perception of categorical \“focal\” colours and their interrelations with varying illuminants and simple chromatic backgrounds. It has been proposed that best examples of colour categories across languages cluster in small regions of the colour space and are restricted to a set of 11 basic terms (Kay and Regier, 2003 Proceedings of the National Academy of Sciences of the USA 100 9085\–9089). Following this, we developed a psychophysical paradigm that exploits the ability of subjects to reliably reproduce the most representative examples of each category, adjusting multiple test patches embedded in a coloured Mondrian. The experiment was run on a CRT monitor (inside a dark room) under various simulated illuminants. We modelled the recorded data for each subject and adapted state as a 3D interconnected structure (graph) in Lab space. The graph nodes were the subject\’s focal colours at each adaptation state. The model allowed us to get a better distance measure between focal structures under different illuminants. We found that perceptual focal structures tend to be preserved better than the structures of the physical \“ideal\” colours under illuminant changes. | |||||
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| Series Editor | Series Title | Perception 40 | Abbreviated Series Title | |||
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| Area | Expedition | Conference | ECVP | |||
| Notes | CIC | Approved | no | |||
| Call Number | Admin @ si @ RPV2011 | Serial | 1867 | |||
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| Author | Javier Vazquez; C. Alejandro Parraga; Maria Vanrell |
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| 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 | C. Alejandro Parraga; Javier Vazquez; Maria Vanrell |
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| Title | A new cone activation-based natural images dataset | Type | Journal Article | |||
| Year | 2009 | Publication | Perception | Abbreviated Journal | PER | |
| Volume | 36 | Issue | Pages |
180 | ||
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| Abstract | We generated a new dataset of digital natural images where each colour plane corresponds to the human LMS (long-, medium-, short-wavelength) cone activations. The images were chosen to represent five different visual environments (eg forest, seaside, mountain snow, urban, motorways) and were taken under natural illumination at different times of day. At the bottom-left corner of each picture there was a matte grey ball of approximately constant spectral reflectance (across the camera's response spectrum,) and nearly Lambertian reflective properties, which allows to compute (and remove, if necessary) the illuminant's colour and intensity. The camera (Sigma Foveon SD10) was calibrated by measuring its sensor's spectral responses using a set of 31 spectrally narrowband interference filters. This allowed conversion of the final camera-dependent RGB colour space into the Smith and Pokorny (1975) cone activation space by means of a polynomial transformation, optimised for a set of 1269 Munsell chip reflectances. This new method is an improvement over the usual 3 × 3 matrix transformation which is only accurate for spectrally-narrowband colours. The camera-to-LMS transformation can be recalculated to consider other non-human visual systems. The dataset is available to download from our website. | |||||
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| Notes | CIC | Approved | no | |||
| Call Number | CAT @ cat @ PVV2009 | Serial | 1193 | |||
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| Author | Jordi Roca; C. Alejandro Parraga; Maria Vanrell |
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| Title | Predicting categorical colour perception in successive colour constancy | Type | Abstract | |||
| Year | 2012 | Publication | Perception | Abbreviated Journal | PER | |
| Volume | 41 | Issue | Pages |
138 | ||
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| Abstract | Colour constancy is a perceptual mechanism that seeks to keep the colour of objects relatively stable under an illumination shift. Experiments haveshown that its effects depend on the number of colours present in the scene. We
studied categorical colour changes under different adaptation states, in particular, whether the colour categories seen under a chromatically neutral illuminant are the same after a shift in the chromaticity of the illumination. To do this, we developed the chromatic setting paradigm (2011 Journal of Vision11 349), which is as an extension of achromatic setting to colour categories. The paradigm exploits the ability of subjects to reliably reproduce the most representative examples of each category, adjusting multiple test patches embedded in a coloured Mondrian. Our experiments were run on a CRT monitor (inside a dark room) under various simulated illuminants and restricting the number of colours of the Mondrian background to three, thus weakening the adaptation effect. Our results show a change in the colour categories present before (under neutral illumination) and after adaptation (under coloured illuminants) with a tendency for adapted colours to be less saturated than before adaptation. This behaviour was predicted by a simple affine matrix model, adjusted to the chromatic setting results. |
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| ISSN | 0301-0066 | ISBN | Medium | |||
| Area | Expedition | Conference | ||||
| Notes | CIC | Approved | no | |||
| Call Number | Admin @ si @ RPV2012 | Serial | 2188 | |||
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| Author | Jaime Moreno; Xavier Otazu; Maria Vanrell |
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| Title | Contribution of CIWaM in JPEG2000 Quantization for Color Images | Type | Conference Article | |||
| Year | 2010 | Publication | Proceedings of The CREATE 2010 Conference | Abbreviated Journal | ||
| Volume | Issue | Pages |
132–136 | |||
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| Abstract | The aim of this work is to explain how to apply perceptual concepts to define a perceptual pre-quantizer and to improve JPEG2000 compressor. The approach consists in quantizing wavelet transform coefficients using some of the human visual system behavior properties. Noise is fatal to image compression performance, because it can be both annoying for the observer and consumes excessive bandwidth when the imagery is transmitted. Perceptual pre-quantization reduces unperceivable details and thus improve both visual impression and transmission properties. The comparison between JPEG2000 without and with perceptual pre-quantization shows that the latter is not favorable in PSNR, but the recovered image is more compressed at the same or even better visual quality measured with a weighted PSNR. Perceptual criteria were taken from the CIWaM(ChromaticInductionWaveletModel). | |||||
| Address | Gjovik (Norway) | |||||
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| Area | Expedition | Conference | CREATE | |||
| Notes | CIC | Approved | no | |||
| Call Number | CAT @ cat @ MOV2010b | Serial | 1308 | |||
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| Author | Agnes Borras; Francesc Tous; Josep Llados; Maria Vanrell |
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| Title | High-Level Clothes Description Based on Color-Texture and Structural Features | Type | Book Chapter | |||
| Year | 2003 | Publication | Lecture Notes in Computer Science | Abbreviated Journal | ||
| Volume | 2652 | Issue | Pages |
108–116 | ||
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| Abstract | This work is a part of a surveillance system where content- based image retrieval is done in terms of people appearance. Given an image of a person, our work provides an automatic description of his clothing according to the colour, texture and structural composition of its garments. We present a two-stage process composed by image segmentation and a region-based interpretation. We segment an image by modelling it due to an attributed graph and applying a hybrid method that follows a split-and-merge strategy. We propose the interpretation of five cloth combinations that are modelled in a graph structure in terms of region features. The interpretation is viewed as a graph matching with an associated cost between the segmentation and the cloth models. Fi- nally, we have tested the process with a ground-truth of one hundred images. | |||||
| Address | Springer-Verlag | |||||
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| Notes | DAG;CIC | Approved | no | |||
| Call Number | CAT @ cat @ BTL2003a | Serial | 368 | |||
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| Author | Olivier Penacchio; C. Alejandro Parraga; Maria Vanrell |
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| Title | Natural Scene Statistics account for Human Cones Ratios | Type | Journal Article | |||
| Year | 2010 | Publication | Perception. ECVP Abstract Supplement | Abbreviated Journal | PER | |
| Volume | 39 | Issue | Pages |
101 | ||
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| Abstract | In two previous experiments [Parraga et al, 2009 J. of Im. Sci. and Tech 53(3) 031106; Benavente et al,2009 Perception 38 ECVP Supplement, 36] the boundaries of basic colour categories were measured.
In the first experiment, samples were presented in isolation (ie on a dark background) and boundaries were measured using a yes/no paradigm. In the second, subjects adjusted the chromaticity of a sample presented on a random Mondrian background to find the boundary between pairs of adjacent colours. Results from these experiments showed significant di erences but it was not possible to conclude whether this discrepancy was due to the absence/presence of a colourful background or to the di erences in the paradigms used. In this work, we settle this question by repeating the first experiment (ie samples presented on a dark background) using the second paradigm. A comparison of results shows that although boundary locations are very similar, boundaries measured in context are significantly di erent(more di use) than those measured in isolation (confirmed by a Student’s t-test analysis on the subject’s answers statistical distributions). In addition, we completed the mapping of colour name space by measuring the boundaries between chromatic colours and the achromatic centre. With these results we completed our parametric fuzzy-sets model of colour naming space. |
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| Notes | CIC | Approved | no | |||
| Call Number | CAT @ cat @ PPV2010 | Serial | 1357 | |||
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| Author | C. Alejandro Parraga; Olivier Penacchio; Maria Vanrell |
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| Title | Retinal Filtering Matches Natural Image Statistics at Low Luminance Levels | Type | Journal Article | |||
| Year | 2011 | Publication | Perception | Abbreviated Journal | PER | |
| Volume | 40 | Issue | Pages |
96 | ||
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| Abstract | The assumption that the retina’s main objective is to provide a minimum entropy representation to higher visual areas (ie efficient coding principle) allows to predict retinal filtering in space–time and colour (Atick, 1992 Network 3 213–251). This is achieved by considering the power spectra of natural images (which is proportional to 1/f2) and the suppression of retinal and image noise. However, most studies consider images within a limited range of lighting conditions (eg near noon) whereas the visual system’s spatial filtering depends on light intensity and the spatiochromatic properties of natural scenes depend of the time of the day. Here, we explore whether the dependence of visual spatial filtering on luminance match the changes in power spectrum of natural scenes at different times of the day. Using human cone-activation based naturalistic stimuli (from the Barcelona Calibrated Images Database), we show that for a range of luminance levels, the shape of the retinal CSF reflects the slope of the power spectrum at low spatial frequencies. Accordingly, the retina implements the filtering which best decorrelates the input signal at every luminance level. This result is in line with the body of work that places efficient coding as a guiding neural principle. | |||||
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| Notes | CIC | Approved | no | |||
| Call Number | Admin @ si @ PPV2011 | Serial | 1720 | |||
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| Author | Robert Benavente; C. Alejandro Parraga; Maria Vanrell |
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| Title | La influencia del contexto en la definicion de las fronteras entre las categorias cromaticas | Type | Conference Article | |||
| Year | 2010 | Publication | 9th Congreso Nacional del Color | Abbreviated Journal | ||
| Volume | Issue | Pages |
92–95 | |||
| Keywords | Categorización del color; Apariencia del color; Influencia del contexto; Patrones de Mondrian; Modelos paramétricos | |||||
| Abstract | En este artículo presentamos los resultados de un experimento de categorización de color en el que las muestras se presentaron sobre un fondo multicolor (Mondrian) para simular los efectos del contexto. Los resultados se comparan con los de un experimento previo que, utilizando un paradigma diferente, determinó las fronteras sin tener en cuenta el contexto. El análisis de los resultados muestra que las fronteras obtenidas con el experimento en contexto presentan menos confusión que las obtenidas en el experimento sin contexto. | |||||
| Address | Alicante (Spain) | |||||
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| ISSN | ISBN | 978-84-9717-144-1 | Medium | |||
| Area | Expedition | Conference | CNC | |||
| Notes | CIC | Approved | no | |||
| Call Number | CAT @ cat @ BPV2010 | Serial | 1327 | |||
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| Author | C. Alejandro Parraga; Robert Benavente; Maria Vanrell |
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| Title | Towards a general model of colour categorization which considers context | Type | Journal Article | |||
| Year | 2010 | Publication | Perception. ECVP Abstract Supplement | Abbreviated Journal | PER | |
| Volume | 39 | Issue | Pages |
86 | ||
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| Abstract | In two previous experiments [Parraga et al, 2009 J. of Im. Sci. and Tech 53(3) 031106; Benavente et al,2009 Perception 38 ECVP Supplement, 36] the boundaries of basic colour categories were measured.
In the first experiment, samples were presented in isolation (ie on a dark background) and boundaries were measured using a yes/no paradigm. In the second, subjects adjusted the chromaticity of a sample presented on a random Mondrian background to find the boundary between pairs of adjacent colours. Results from these experiments showed significant di erences but it was not possible to conclude whether this discrepancy was due to the absence/presence of a colourful background or to the di erences in the paradigms used. In this work, we settle this question by repeating the first experiment (ie samples presented on a dark background) using the second paradigm. A comparison of results shows that although boundary locations are very similar, boundaries measured in context are significantly di erent(more di use) than those measured in isolation (confirmed by a Student’s t-test analysis on the subject’s answers statistical distributions). In addition, we completed the mapping of colour name space by measuring the boundaries between chromatic colours and the achromatic centre. With these results we completed our parametric fuzzy-sets model of colour naming space. |
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| Notes | CIC | Approved | no | |||
| Call Number | CAT @ cat @ PBV2010b | Serial | 1326 | |||
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