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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 | Alicia Fornes; Josep Llados; Gemma Sanchez; Xavier Otazu; Horst Bunke |
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Title | A Combination of Features for Symbol-Independent Writer Identification in Old Music Scores | Type | 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 | |||
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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 |
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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 dierences but it was not possible to conclude whether this discrepancy was due to the absence/presence of a colourful background or to the dierences 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 dierent(more diuse) 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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Author | Javier Vazquez; Maria Vanrell; Robert Benavente |
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Title | Color names as a constraint for Computer Vision problems | Type | Conference Article | |||
Year | 2010 | Publication | Proceedings of The CREATE 2010 Conference | Abbreviated Journal | ||
Volume | Issue | Pages | 324–328 | |||
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Abstract | Computer Vision Problems are usually ill-posed. Constraining de gamut of possible solutions is then a necessary step. Many constrains for different problems have been developed during years. In this paper, we present a different way of constraining some of these problems: the use of color names. In particular, we will focus on segmentation, representation ans constancy. | |||||
Address | Gjovik (Norway) | |||||
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Area | Expedition | Conference | CREATE | |||
Notes | CIC | Approved | no | |||
Call Number | CAT @ cat @ VVB2010 | Serial | 1328 | |||
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Author | Fahad Shahbaz Khan; Joost Van de Weijer; Maria Vanrell |
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Title | Who Painted this Painting? | Type | Conference Article | |||
Year | 2010 | Publication | Proceedings of The CREATE 2010 Conference | Abbreviated Journal | ||
Volume | Issue | Pages | 329–333 | |||
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Address | Gjovik (Norway) | |||||
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Area | Expedition | Conference | CREATE | |||
Notes | CIC | Approved | no | |||
Call Number | CAT @ cat @ KWV2010 | Serial | 1329 | |||
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Author | Shida Beigpour; Joost Van de Weijer |
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Title | Photo-Realistic Color Alteration for Architecture and Design | Type | Conference Article | |||
Year | 2010 | Publication | Proceedings of The CREATE 2010 Conference | Abbreviated Journal | ||
Volume | Issue | Pages | 84–88 | |||
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Abstract | As color is a strong stimuli we receive from the exterior world, choosing the right color can prove crucial in creating the desired architecture and desing. We propose a framework to apply a realistic color change on both objects and their illuminant lights for snapshots of architectural designs, in order to visualize and choose the right color before actully applying the change in the real world. The proposed framework is based on the laws of physics in order to accomplish realistic and physically plausible results. | |||||
Address | Gjovik (Norway) | |||||
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Area | Expedition | Conference | CREATE | |||
Notes | CIC | Approved | no | |||
Call Number | CAT @ cat @ BeW2010 | Serial | 1330 | |||
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Author | Marc Serra |
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Title | Estimating Intrinsic Images from Physical and Categorical Color Cues | Type | Report | |||
Year | 2010 | Publication | CVC Technical Report | Abbreviated Journal | ||
Volume | 151 | Issue | Pages | |||
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Corporate Author | Thesis | Master's thesis | ||||
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Notes | CIC | Approved | no | |||
Call Number | Admin @ si @ Ser2010 | Serial | 1345 | |||
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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 dierences but it was not possible to conclude whether this discrepancy was due to the absence/presence of a colourful background or to the dierences 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 dierent(more diuse) 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 | Xavier Otazu; C. Alejandro Parraga; Maria Vanrell |
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Title | Towards a unified chromatic inducction model | Type | Journal Article | |||
Year | 2010 | Publication | Journal of Vision | Abbreviated Journal | VSS | |
Volume | 10 | Issue | 12:5 | Pages | 1-24 | |
Keywords | Visual system; Color induction; Wavelet transform | |||||
Abstract | In a previous work (X. Otazu, M. Vanrell, & C. A. Párraga, 2008b), we showed how several brightness induction effects can be predicted using a simple multiresolution wavelet model (BIWaM). Here we present a new model for chromatic induction processes (termed Chromatic Induction Wavelet Model or CIWaM), which is also implemented on a multiresolution framework and based on similar assumptions related to the spatial frequency and the contrast surround energy of the stimulus. The CIWaM can be interpreted as a very simple extension of the BIWaM to the chromatic channels, which in our case are defined in the MacLeod-Boynton (lsY) color space. This new model allows us to unify both chromatic assimilation and chromatic contrast effects in a single mathematical formulation. The predictions of the CIWaM were tested by means of several color and brightness induction experiments, which showed an acceptable agreement between model predictions and psychophysical data. | |||||
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Notes | CIC | Approved | no | |||
Call Number | CAT @ cat @ OPV2010 | Serial | 1450 | |||
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Author | Enric Marti; Jordi Rocarias; Ricardo Toledo |
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Title | Caront: gestió flexible de grups d’alumnes en una asignatura i activitats sobre grups. Nova activitat de control | Type | Miscellaneous | |||
Year | 2008 | Publication | V Jornades d’Innovació Docent | Abbreviated Journal | ||
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Notes | IAM;RV;CIC;ADAS | Approved | no | |||
Call Number | IAM @ iam @ MRT2008a | Serial | 1617 | |||
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Author | Ernest Valveny; Ricardo Toledo; Ramon Baldrich; Enric Marti |
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Title | Combining recognition-based in segmentation-based approaches for graphic symol recognition using deformable template matching | Type | Conference Article | |||
Year | 2002 | Publication | Proceeding of the Second IASTED International Conference Visualization, Imaging and Image Proceesing VIIP 2002 | Abbreviated Journal | ||
Volume | Issue | Pages | 502–507 | |||
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Notes | DAG;RV;CAT;IAM;CIC;ADAS | Approved | no | |||
Call Number | IAM @ iam @ VTB2002 | Serial | 1660 | |||
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Author | Eduard Vazquez; Ramon Baldrich; Joost Van de Weijer; Maria Vanrell |
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Title | Describing Reflectances for Colour Segmentation Robust to Shadows, Highlights and Textures | Type | Journal Article | |||
Year | 2011 | Publication | IEEE Transactions on Pattern Analysis and Machine Intelligence | Abbreviated Journal | TPAMI | |
Volume | 33 | Issue | 5 | Pages | 917-930 | |
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Abstract | The segmentation of a single material reflectance is a challenging problem due to the considerable variation in image measurements caused by the geometry of the object, shadows, and specularities. The combination of these effects has been modeled by the dichromatic reflection model. However, the application of the model to real-world images is limited due to unknown acquisition parameters and compression artifacts. In this paper, we present a robust model for the shape of a single material reflectance in histogram space. The method is based on a multilocal creaseness analysis of the histogram which results in a set of ridges representing the material reflectances. The segmentation method derived from these ridges is robust to both shadow, shading and specularities, and texture in real-world images. We further complete the method by incorporating prior knowledge from image statistics, and incorporate spatial coherence by using multiscale color contrast information. Results obtained show that our method clearly outperforms state-of-the-art segmentation methods on a widely used segmentation benchmark, having as a main characteristic its excellent performance in the presence of shadows and highlights at low computational cost. | |||||
Address | Los Alamitos; CA; USA; | |||||
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Publisher | IEEE Computer Society | Place of Publication | Editor | |||
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ISSN | 0162-8828 | ISBN | Medium | |||
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Notes | CIC | Approved | no | |||
Call Number | Admin @ si @ VBW2011 | Serial | 1715 | |||
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Author | Arjan Gijsenij; Theo Gevers; Joost Van de Weijer |
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Title | Computational Color Constancy: Survey and Experiments | Type | Journal Article | |||
Year | 2011 | Publication | IEEE Transactions on Image Processing | Abbreviated Journal | TIP | |
Volume | 20 | Issue | 9 | Pages | 2475-2489 | |
Keywords | computational color constancy;computer vision application;gamut-based method;learning-based method;static method;colour vision;computer vision;image colour analysis;learning (artificial intelligence);lighting | |||||
Abstract | Computational color constancy is a fundamental prerequisite for many computer vision applications. This paper presents a survey of many recent developments and state-of-the- art methods. Several criteria are proposed that are used to assess the approaches. A taxonomy of existing algorithms is proposed and methods are separated in three groups: static methods, gamut-based methods and learning-based methods. Further, the experimental setup is discussed including an overview of publicly available data sets. Finally, various freely available methods, of which some are considered to be state-of-the-art, are evaluated on two data sets. | |||||
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ISSN | 1057-7149 | ISBN | Medium | |||
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Notes | ISE;CIC | Approved | no | |||
Call Number | Admin @ si @ GGW2011 | Serial | 1717 | |||
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Author | Xavier Boix; Josep M. Gonfaus; Joost Van de Weijer; Andrew Bagdanov; Joan Serrat; Jordi Gonzalez |
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Title | Harmony Potentials: Fusing Global and Local Scale for Semantic Image Segmentation | Type | Journal Article | |||
Year | 2012 | Publication | International Journal of Computer Vision | Abbreviated Journal | IJCV | |
Volume | 96 | Issue | 1 | Pages | 83-102 | |
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Abstract | The Hierarchical Conditional Random Field(HCRF) model have been successfully applied to a number of image labeling problems, including image segmentation. However, existing HCRF models of image segmentation do not allow multiple classes to be assigned to a single region, which limits their ability to incorporate contextual information across multiple scales.
At higher scales in the image, this representation yields an oversimplied model since multiple classes can be reasonably expected to appear within large regions. This simplied model particularly limits the impact of information at higher scales. Since class-label information at these scales is usually more reliable than at lower, noisier scales, neglecting this information is undesirable. To address these issues, we propose a new consistency potential for image labeling problems, which we call the harmony potential. It can encode any possible combi- nation of labels, penalizing only unlikely combinations of classes. We also propose an eective sampling strategy over this expanded label set that renders tractable the underlying optimization problem. Our approach obtains state-of-the-art results on two challenging, standard benchmark datasets for semantic image segmentation: PASCAL VOC 2010, and MSRC-21. |
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ISSN | 0920-5691 | ISBN | Medium | |||
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Notes | ISE;CIC;ADAS | Approved | no | |||
Call Number | Admin @ si @ BGW2012 | Serial | 1718 | |||
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Author | Olivier Penacchio; C. Alejandro Parraga |
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Title | What is the best criterion for an efficient design of retinal photoreceptor mosaics? | Type | Journal Article | |||
Year | 2011 | Publication | Perception | Abbreviated Journal | PER | |
Volume | 40 | Issue | Pages | 197 | ||
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Abstract | The proportions of L, M and S photoreceptors in the primate retina are arguably determined by evolutionary pressure and the statistics of the visual environment. Two information theory-based approaches have been recently proposed for explaining the asymmetrical spatial densities of photoreceptors in humans. In the first approach Garrigan et al (2010 PLoS ONE 6 e1000677), a model for computing the information transmitted by cone arrays which considers the differential blurring produced by the long-wavelength accommodation of the eye’s lens is proposed. Their results explain the sparsity of S-cones but the optimum depends weakly on the L:M cone ratio. In the second approach (Penacchio et al, 2010 Perception 39 ECVP Supplement, 101), we show that human cone arrays make the visual representation scale-invariant, allowing the total entropy of the signal to be preserved while decreasing individual neurons’ entropy in further retinotopic representations. This criterion provides a thorough description of the distribution of L:M cone ratios and does not depend on differential blurring of the signal by the lens. Here, we investigate the similarities and differences of both approaches when applied to the same database. Our results support a 2-criteria optimization in the space of cone ratios whose components are arguably important and mostly unrelated.
[This work was partially funded by projects TIN2010-21771-C02-1 and Consolider-Ingenio 2010-CSD2007-00018 from the Spanish MICINN. CAP was funded by grant RYC-2007-00484] |
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Notes | CIC | Approved | no | |||
Call Number | Admin @ si @ PeP2011a | Serial | 1719 | |||
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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 | Olivier Penacchio |
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Title | Mixed Hodge Structures and Equivariant Sheaves on the Projective Plane | Type | Journal Article | |||
Year | 2011 | Publication | Mathematische Nachrichten | Abbreviated Journal | MN | |
Volume | 284 | Issue | 4 | Pages | 526-542 | |
Keywords | Mixed Hodge structures, equivariant sheaves, MSC (2010) Primary: 14C30, Secondary: 14F05, 14M25 | |||||
Abstract | We describe an equivalence of categories between the category of mixed Hodge structures and a category of equivariant vector bundles on a toric model of the complex projective plane which verify some semistability condition. We then apply this correspondence to define an invariant which generalizes the notion of R-split mixed Hodge structure and give calculations for the first group of cohomology of possibly non smooth or non-complete curves of genus 0 and 1. Finally, we describe some extension groups of mixed Hodge structures in terms of equivariant extensions of coherent sheaves. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim | |||||
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Publisher | WILEY-VCH Verlag | Place of Publication | Editor | R. Mennicken | ||
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ISSN | 1522-2616 | ISBN | Medium | |||
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Notes | CIC | Approved | no | |||
Call Number | Admin @ si @ Pen2011 | Serial | 1721 | |||
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Author | Jordi Roca; A.Owen; G.Jordan; Y.Ling; C. Alejandro Parraga; A.Hurlbert |
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Title | Inter-individual Variations in Color Naming and the Structure of 3D Color Space | Type | Abstract | |||
Year | 2011 | Publication | Journal of Vision | Abbreviated Journal | VSS | |
Volume | 12 | Issue | 2 | Pages | 166 | |
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Abstract | 36.307
Many everyday behavioural uses of color vision depend on color naming ability, which is neither measured nor predicted by most standardized tests of color vision, for either normal or anomalous color vision. Here we demonstrate a new method to quantify color naming ability by deriving a compact computational description of individual 3D color spaces. Methods: Individual observers underwent standardized color vision diagnostic tests (including anomaloscope testing) and a series of custom-made color naming tasks using 500 distinct color samples, either CRT stimuli (“light”-based) or Munsell chips (“surface”-based), with both forced- and free-choice color naming paradigms. For each subject, we defined his/her color solid as the set of 3D convex hulls computed for each basic color category from the relevant collection of categorised points in perceptually uniform CIELAB space. From the parameters of the convex hulls, we derived several indices to characterise the 3D structure of the color solid and its inter-individual variations. Using a reference group of 25 normal trichromats (NT), we defined the degree of normality for the shape, location and overlap of each color region, and the extent of “light”-“surface” agreement. Results: Certain features of color perception emerge from analysis of the average NT color solid, e.g.: (1) the white category is slightly shifted towards blue; and (2) the variability in category border location across NT subjects is asymmetric across color space, with least variability in the blue/green region. Comparisons between individual and average NT indices reveal specific naming “deficits”, e.g.: (1) Category volumes for white, green, brown and grey are expanded for anomalous trichromats and dichromats; and (2) the focal structure of color space is disrupted more in protanopia than other forms of anomalous color vision. The indices both capture the structure of subjective color spaces and allow us to quantify inter-individual differences in color naming ability. |
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ISSN | 1534-7362 | ISBN | Medium | |||
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Notes | CIC | Approved | no | |||
Call Number | Admin @ si @ ROJ2011 | Serial | 1758 | |||
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