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Author | Robert Benavente; C. Alejandro Parraga; Maria Vanrell | ||||
Title | Colour categories boundaries are better defined in contextual conditions | Type | 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 | 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 | Naila Murray; Eduard Vazquez | ||||
Title | Lacuna Restoration: How to choose a neutral colour? | Type | Conference Article | ||
Year | 2010 | Publication | Proceedings of The CREATE 2010 Conference | Abbreviated Journal | |
Volume | Issue | Pages | 248–252 | ||
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Abstract | Painting restoration which involves filling in material loss (called lacuna) is a complex process. Several standard techniques exist to tackle lacuna restoration,
and this article focuses on those techniques that employ a “neutral” colour to mask the defect. Restoration experts often disagree on the choice of such a colour and in fact, the concept of a neutral colour is controversial. We posit that a neutral colour is one that attracts relatively little visual attention for a specific lacuna. We conducted an eye tracking experiment to compare two common neutral colour selection methods, specifically the most common local colour and the mean local colour. Results obtained demonstrate that the most common local colour triggers less visual attention in general. Notwithstanding, we have observed instances in which the most common colour triggers a significant amount of attention when subjects spent time resolving their confusion about whether or not a lacuna was part of the painting. |
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Address | Gjovik, Norway | ||||
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Area | Expedition | Conference | CREATE | ||
Notes | CIC | Approved | no | ||
Call Number | Admin @ si @ MuV2010 | Serial | 1297 | ||
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Author | Eduard Vazquez; Ramon Baldrich | ||||
Title | Non-supervised goodness measure for image segmentation | Type | Conference Article | ||
Year | 2010 | Publication | Proceedings of The CREATE 2010 Conference | Abbreviated Journal | |
Volume | Issue | Pages | 334–335 | ||
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Address | Gjovik, Norway | ||||
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Area | Expedition | Conference | CREATE | ||
Notes | CIC | Approved | no | ||
Call Number | CAT @ cat @ VaB2010 | Serial | 1299 | ||
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Author | Jaime Moreno; Xavier Otazu; Maria Vanrell | ||||
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 | ||||
Corporate Author | Thesis | ||||
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Language | Summary Language | Original Title | |||
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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 | Jaime Moreno; Xavier Otazu; Maria Vanrell | ||||
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 | C. Alejandro Parraga; Ramon Baldrich; Maria Vanrell | ||||
Title | Accurate Mapping of Natural Scenes Radiance to Cone Activation Space: A New Image Dataset | 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 | 50–57 | ||
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Abstract | The characterization of trichromatic cameras is usually done in terms of a device-independent color space, such as the CIE 1931 XYZ space. This is indeed convenient since it allows the testing of results against colorimetric measures. We have characterized our camera to represent human cone activation by mapping the camera sensor's (RGB) responses to human (LMS) through a polynomial transformation, which can be “customized” according to the types of scenes we want to represent. Here we present a method to test the accuracy of the camera measures and a study on how the choice of training reflectances for the polynomial may alter the results. | ||||
Address | Joensuu, Finland | ||||
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ISSN | ISBN | 9781617388897 | Medium | ||
Area | Expedition | Conference | CGIV/MCS | ||
Notes | CIC | Approved | no | ||
Call Number | CAT @ cat @ PBV2010a | Serial | 1322 | ||
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Author | 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. |
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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 | Javier Vazquez; Maria Vanrell; Robert Benavente | ||||
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 | ||||
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 | ||||
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 | ||||
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 | ||||
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 | Enric Marti; Jordi Rocarias; Ricardo Toledo | ||||
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 | ||||
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 | C. Alejandro Parraga; Olivier Penacchio; Maria Vanrell | ||||
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 | 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 | Eduard Vazquez | ||||
Title | Unsupervised image segmentation based on material reflectance description and saliency | Type | Book Whole | ||
Year | 2011 | Publication | PhD Thesis, Universitat Autonoma de Barcelona-CVC | Abbreviated Journal | |
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Abstract | Image segmentations aims to partition an image into a set of non-overlapped regions, called segments. Despite the simplicity of the definition, image segmentation raises as a very complex problem in all its stages. The definition of segment is still unclear. When asking to a human to perform a segmentation, this person segments at different levels of abstraction. Some segments might be a single, well-defined texture whereas some others correspond with an object in the scene which might including multiple textures and colors. For this reason, segmentation is divided in bottom-up segmentation and top-down segmentation. Bottom up-segmentation is problem independent, that is, focused on general properties of the images such as textures or illumination. Top-down segmentation is a problem-dependent approach which looks for specific entities in the scene, such as known objects. This work is focused on bottom-up segmentation. Beginning from the analysis of the lacks of current methods, we propose an approach called RAD. Our approach overcomes the main shortcomings of those methods which use the physics of the light to perform the segmentation. RAD is a topological approach which describes a single-material reflectance. Afterwards, we cope with one of the main problems in image segmentation: non supervised adaptability to image content. To yield a non-supervised method, we use a model of saliency yet presented in this thesis. It computes the saliency of the chromatic transitions of an image by means of a statistical analysis of the images derivatives. This method of saliency is used to build our final approach of segmentation: spRAD. This method is a non-supervised segmentation approach. Our saliency approach has been validated with a psychophysical experiment as well as computationally, overcoming a state-of-the-art saliency method. spRAD also outperforms state-of-the-art segmentation techniques as results obtained with a widely-used segmentation dataset show | ||||
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Corporate Author | Thesis | Ph.D. thesis | |||
Publisher | Place of Publication | Editor | Ramon Baldrich | ||
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Notes | CIC | Approved | no | ||
Call Number | Admin @ si @ Vaz2011b | Serial | 1835 | ||
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