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Author O. Fors; A. Richichi; Xavier Otazu; J. Nuñez
Title A new wavelet-based approach for the automated treatment of large sets of lunar occultation data Type (up) Journal
Year 2008 Publication Astronomy and Astrohysics Abbreviated Journal
Volume 480 Issue Pages 297–304
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Notes CIC Approved no
Call Number CAT @ cat @ FRO2008 Serial 934
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Author Robert Benavente; Maria Vanrell; Ramon Baldrich
Title Parametric Fuzzy Sets for Automatic Color Naming Type (up) Journal
Year 2008 Publication Journal of the Optical Society of America A Abbreviated Journal
Volume 25 Issue 10 Pages 2582–2593
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Notes CIC Approved no
Call Number CAT @ cat @ BVB2008 Serial 1004
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Author Xavier Otazu; Maria Vanrell; C. Alejandro Parraga
Title Colour induction effects are modelled by a low-level multiresolution wavelet framework Type (up) Journal
Year 2008 Publication Perception 37(Suppl.): 107 Abbreviated Journal
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Notes CIC Approved no
Call Number CAT @ cat @ OVP2008b Serial 1055
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Author Yasuko Sugito; Trevor Canham; Javier Vazquez; Marcelo Bertalmio
Title A Study of Objective Quality Metrics for HLG-Based HDR/WCG Image Coding Type (up) Journal
Year 2021 Publication SMPTE Motion Imaging Journal Abbreviated Journal SMPTE
Volume 130 Issue 4 Pages 53 - 65
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Abstract In this work, we study the suitability of high dynamic range, wide color gamut (HDR/WCG) objective quality metrics to assess the perceived deterioration of compressed images encoded using the hybrid log-gamma (HLG) method, which is the standard for HDR television. Several image quality metrics have been developed to deal specifically with HDR content, although in previous work we showed that the best results (i.e., better matches to the opinion of human expert observers) are obtained by an HDR metric that consists simply in applying a given standard dynamic range metric, called visual information fidelity (VIF), directly to HLG-encoded images. However, all these HDR metrics ignore the chroma components for their calculations, that is, they consider only the luminance channel. For this reason, in the current work, we conduct subjective evaluation experiments in a professional setting using compressed HDR/WCG images encoded with HLG and analyze the ability of the best HDR metric to detect perceivable distortions in the chroma components, as well as the suitability of popular color metrics (including ΔITPR , which supports parameters for HLG) to correlate with the opinion scores. Our first contribution is to show that there is a need to consider the chroma components in HDR metrics, as there are color distortions that subjects perceive but that the best HDR metric fails to detect. Our second contribution is the surprising result that VIF, which utilizes only the luminance channel, correlates much better with the subjective evaluation scores than the metrics investigated that do consider the color components.
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Notes CIC Approved no
Call Number SCV2021 Serial 3671
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Author Maria Vanrell; Jordi Vitria; Xavier Roca
Title A multidimensional scaling approach to explore the behavior of a texture perception algorithm. Type (up) 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 Judit Martinez; Eva Costa; P. Herreros; F. Javier Sanchez; Ramon Baldrich
Title A Modular and Scalable Architecture for PC-Based Real-Time Vision Systems Type (up) Journal Article
Year 2003 Publication Real–Time Imaging, (IF: 0.512) Abbreviated Journal
Volume 9 Issue Pages 99-112
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Notes CIC Approved no
Call Number CAT @ cat @ MCH2003b Serial 394
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Author Daniel Ponsa; Robert Benavente; Felipe Lumbreras; Judit Martinez; Xavier Roca
Title Quality control of safety belts by machine vision inspection for real-time production Type (up) Journal Article
Year 2003 Publication Optical Engineering (IF: 0.877) Abbreviated Journal
Volume 42 Issue 4 Pages 1114-1120
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Publisher SPIE Place of Publication Editor
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Notes ADAS;ISE;CIC Approved no
Call Number ADAS @ adas @ PRL2003 Serial 399
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Author Xavier Otazu; Oriol Pujol
Title Wavelet based approach to cluster analysis. Application on low dimensional data sets Type (up) Journal Article
Year 2006 Publication Pattern Recognition Letters Abbreviated Journal PRL
Volume 27 Issue 14 Pages 1590–1605
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Notes MILAB; CIC; HuPBA Approved no
Call Number BCNPCL @ bcnpcl @ OtP2006 Serial 658
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Author T. Widemann; Xavier Otazu
Title Titanias radius and an upper limit on its atmosphere from the September 8, 2001 stellar occultation Type (up) Journal Article
Year 2009 Publication International Journal of Solar System Studies Abbreviated Journal
Volume 199 Issue 2 Pages 458–476
Keywords Occultations; Uranus, satellites; Satellites, shapes; Satellites, dynamics; Ices; Satellites, atmospheres
Abstract On September 8, 2001 around 2 h UT, the largest uranian moon, Titania, occulted Hipparcos star 106829 (alias SAO 164538, a V=7.2, K0 III star). This was the first-ever observed occultation by this satellite, a rare event as Titania subtends only 0.11 arcsec on the sky. The star's unusual brightness allowed many observers, both amateurs or professionals, to monitor this unique event, providing fifty-seven occultations chords over three continents, all reported here. Selecting the best 27 occultation chords, and assuming a circular limb, we derive Titania's radius: View the MathML source (1-σ error bar). This implies a density of View the MathML source using the value View the MathML source derived by Taylor [Taylor, D.B., 1998. Astron. Astrophys. 330, 362–374]. We do not detect any significant difference between equatorial and polar radii, in the limit View the MathML source, in agreement with Voyager limb image retrieval during the 1986 flyby. Titania's offset with respect to the DE405 + URA027 (based on GUST86 theory) ephemeris is derived: ΔαTcos(δT)=−108±13 mas and ΔδT=−62±7 mas (ICRF J2000.0 system). Most of this offset is attributable to a Uranus' barycentric offset with respect to DE405, that we estimate to be: View the MathML source and ΔδU=−85±25 mas at the moment of occultation. This offset is confirmed by another Titania stellar occultation observed on August 1st, 2003, which provides an offset of ΔαTcos(δT)=−127±20 mas and ΔδT=−97±13 mas for the satellite. The combined ingress and egress data do not show any significant hint for atmospheric refraction, allowing us to set surface pressure limits at the level of 10–20 nbar. More specifically, we find an upper limit of 13 nbar (1-σ level) at 70 K and 17 nbar at 80 K, for a putative isothermal CO2 atmosphere. We also provide an upper limit of 8 nbar for a possible CH4 atmosphere, and 22 nbar for pure N2, again at the 1-σ level. We finally constrain the stellar size using the time-resolved star disappearance and reappearance at ingress and egress. We find an angular diameter of 0.54±0.03 mas (corresponding to View the MathML source projected at Titania). With a distance of 170±25 parsecs, this corresponds to a radius of 9.8±0.2 solar radii for HIP 106829, typical of a K0 III giant.
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Publisher ELSEVIER Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0019-1035 ISBN Medium
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Notes CIC Approved no
Call Number CAT @ cat @ Wid2009 Serial 1052
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Author C. Alejandro Parraga; Robert Benavente; Maria Vanrell; Ramon Baldrich
Title Psychophysical measurements to model inter-colour regions of colour-naming space Type (up) Journal Article
Year 2009 Publication Journal of Imaging Science and Technology Abbreviated Journal
Volume 53 Issue 3 Pages 031106 (8 pages)
Keywords image processing; Analysis
Abstract JCR Impact Factor 2009: 0.391
In this paper, we present a fuzzy-set of parametric functions which segment the CIE lab space into eleven regions which correspond to the group of common universal categories present in all evolved languages as identified by anthropologists and linguists. The set of functions is intended to model a color-name assignment task by humans and differs from other models in its emphasis on the inter-color boundary regions, which were explicitly measured by means of a psychophysics experiment. In our particular implementation, the CIE lab space was segmented into eleven color categories using a Triple Sigmoid as the fuzzy sets basis, whose parameters are included in this paper. The model’s parameters were adjusted according to the psychophysical results of a yes/no discrimination paradigm where observers had to choose (English) names for isoluminant colors belonging to regions in-between neighboring categories. These colors were presented on a calibrated CRT monitor (14-bit x 3 precision). The experimental results show that inter- color boundary regions are much less defined than expected and color samples other than those near the most representatives are needed to define the position and shape of boundaries between categories. The extended set of model parameters is given as a table.
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Notes CIC Approved no
Call Number CAT @ cat @ PBV2009 Serial 1157
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Author Javier Vazquez; C. Alejandro Parraga; Maria Vanrell; Ramon Baldrich
Title Color Constancy Algorithms: Psychophysical Evaluation on a New Dataset Type (up) 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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Notes CIC Approved no
Call Number CAT @ cat @ VPV2009a Serial 1171
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Author Javier Vazquez; C. Alejandro Parraga; Maria Vanrell
Title Ordinal pairwise method for natural images comparison Type (up) 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 Robert Benavente; C. Alejandro Parraga; Maria Vanrell
Title Colour categories boundaries are better defined in contextual conditions Type (up) Journal Article
Year 2009 Publication Perception Abbreviated Journal PER
Volume 38 Issue Pages 36
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Abstract In a previous experiment [Parraga et al, 2009 Journal of Imaging Science and Technology 53(3)] the boundaries between basic colour categories were measured by asking subjects to categorize colour samples presented in isolation (ie on a dark background) using a YES/NO paradigm. Results showed that some boundaries (eg green – blue) were very diffuse and the subjects' answers presented bimodal distributions, which were attributed to the emergence of non-basic categories in those regions (eg turquoise). To confirm these results we performed a new experiment focussed on the boundaries where bimodal distributions were more evident. In this new experiment rectangular colour samples were presented surrounded by random colour patches to simulate contextual conditions on a calibrated CRT monitor. The names of two neighbouring colours were shown at the bottom of the screen and subjects selected the boundary between these colours by controlling the chromaticity of the central patch, sliding it across these categories' frontier. Results show that in this new experimental paradigm, the formerly uncertain inter-colour category boundaries are better defined and the dispersions (ie the bimodal distributions) that occurred in the previous experiment disappear. These results may provide further support to Berlin and Kay's basic colour terms theory.
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Notes CIC Approved no
Call Number CAT @ cat @ BPV2009 Serial 1192
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Author C. Alejandro Parraga; Javier Vazquez; Maria Vanrell
Title A new cone activation-based natural images dataset Type (up) 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 Eduard Vazquez; Theo Gevers; M. Lucassen; Joost Van de Weijer; Ramon Baldrich
Title Saliency of Color Image Derivatives: A Comparison between Computational Models and Human Perception Type (up) Journal Article
Year 2010 Publication Journal of the Optical Society of America A Abbreviated Journal JOSA A
Volume 27 Issue 3 Pages 613–621
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Abstract In this paper, computational methods are proposed to compute color edge saliency based on the information content of color edges. The computational methods are evaluated on bottom-up saliency in a psychophysical experiment, and on a more complex task of salient object detection in real-world images. The psychophysical experiment demonstrates the relevance of using information theory as a saliency processing model and that the proposed methods are significantly better in predicting color saliency (with a human-method correspondence up to 74.75% and an observer agreement of 86.8%) than state-of-the-art models. Furthermore, results from salient object detection confirm that an early fusion of color and contrast provide accurate performance to compute visual saliency with a hit rate up to 95.2%.
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Notes ISE;CIC Approved no
Call Number CAT @ cat @ VGL2010 Serial 1275
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Author O. Fors; J. Nuñez; Xavier Otazu; A. Prades; Robert D. Cardinal
Title Improving the Ability of Image Sensors to Detect Faint Stars and Moving Objects Using Image Deconvolution Techniques Type (up) Journal Article
Year 2010 Publication Sensors Abbreviated Journal SENS
Volume 10 Issue 3 Pages 1743–1752
Keywords image processing; image deconvolution; faint stars; space debris; wavelet transform
Abstract Abstract: In this paper we show how the techniques of image deconvolution can increase the ability of image sensors as, for example, CCD imagers, to detect faint stars or faint orbital objects (small satellites and space debris). In the case of faint stars, we show that this benefit is equivalent to double the quantum efficiency of the used image sensor or to increase the effective telescope aperture by more than 30% without decreasing the astrometric precision or introducing artificial bias. In the case of orbital objects, the deconvolution technique can double the signal-to-noise ratio of the image, which helps to discover and control dangerous objects as space debris or lost satellites. The benefits obtained using CCD detectors can be extrapolated to any kind of image sensors.
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Notes CIC Approved no
Call Number CAT @ cat @ FNO2010 Serial 1285
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Author Alicia Fornes; Josep Llados; Gemma Sanchez; Xavier Otazu; Horst Bunke
Title A Combination of Features for Symbol-Independent Writer Identification in Old Music Scores Type (up) Journal Article
Year 2010 Publication International Journal on Document Analysis and Recognition Abbreviated Journal IJDAR
Volume 13 Issue 4 Pages 243-259
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Abstract The aim of writer identification is determining the writer of a piece of handwriting from a set of writers. In this paper, we present an architecture for writer identification in old handwritten music scores. Even though an important amount of music compositions contain handwritten text, the aim of our work is to use only music notation to determine the author. The main contribution is therefore the use of features extracted from graphical alphabets. Our proposal consists in combining the identification results of two different approaches, based on line and textural features. The steps of the ensemble architecture are the following. First of all, the music sheet is preprocessed for removing the staff lines. Then, music lines and texture images are generated for computing line features and textural features. Finally, the classification results are combined for identifying the writer. The proposed method has been tested on a database of old music scores from the seventeenth to nineteenth centuries, achieving a recognition rate of about 92% with 20 writers.
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Publisher Springer-Verlag Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 1433-2833 ISBN Medium
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Notes DAG; CAT;CIC Approved no
Call Number FLS2010b Serial 1319
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Author C. Alejandro Parraga; Robert Benavente; Maria Vanrell
Title Towards a general model of colour categorization which considers context Type (up) Journal Article
Year 2010 Publication Perception. ECVP Abstract Supplement Abbreviated Journal PER
Volume 39 Issue Pages 86
Keywords
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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