A spatial processor model for object colour perception
01 Jul 1980-Journal of The Franklin Institute-engineering and Applied Mathematics (Pergamon)-Vol. 310, Iss: 1, pp 1-26
TL;DR: In this article, a comprehensive mathematical model to account for colour constancy is formulated, where the visual system is able to measure true object colour in complex scenes under a broad range of spectral compositions, for the illumination; it is assumed that the visual systems must implicitly estimate and illuminant.
Abstract: A comprehensive mathematical model to account for colour constancy is formulated. Since the visual system is able to measure true object colour in complex scenes under a broad range of spectral compositions, for the illumination; it is assumed that the visual system must implicitly estimate and illuminant. The basic hypothesis is that the estimate of the illuminant is made on the basis of spatial information from the entire visual field. This estimate is then used by the visual system to arrive at an estimate of the (object) reflectance of the various subfields in the complex visual scene. The estimates are made by matching the inputs to the system to linear combinations of fixed bases and standards in the colour space. The model provides a general unified mathematical framework for related psychophysical phenomenology.
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TL;DR: Experiments on a number of challenging low-light images are present to reveal the efficacy of the proposed LIME and show its superiority over several state-of-the-arts in terms of enhancement quality and efficiency.
Abstract: When one captures images in low-light conditions, the images often suffer from low visibility. Besides degrading the visual aesthetics of images, this poor quality may also significantly degenerate the performance of many computer vision and multimedia algorithms that are primarily designed for high-quality inputs. In this paper, we propose a simple yet effective low-light image enhancement (LIME) method. More concretely, the illumination of each pixel is first estimated individually by finding the maximum value in R, G, and B channels. Furthermore, we refine the initial illumination map by imposing a structure prior on it, as the final illumination map. Having the well-constructed illumination map, the enhancement can be achieved accordingly. Experiments on a number of challenging low-light images are present to reveal the efficacy of our LIME and show its superiority over several state-of-the-arts in terms of enhancement quality and efficiency.
1,364 citations
TL;DR: A critical up-to-date review of the various skin modeling and classification strategies based on color information in the visual spectrum and presents various approaches that use skin-color constancy and dynamic adaptation techniques to improve the skin detection performance in dynamically changing illumination and environmental conditions.
996 citations
TL;DR: A computational method for estimating surface spectral reflectance when the spectral power distribution of the ambient light is not known is described, which can be reliably estimated despite changes in the ambient lighting conditions.
Abstract: Human and machine visual sensing is enhanced when surface properties of objects in scenes, including color, can be reliably estimated despite changes in the ambient lighting conditions. We describe a computational method for estimating surface spectral reflectance when the spectral power distribution of the ambient light is not known.
840 citations
Cites background or methods from "A spatial processor model for objec..."
...We consider the limits on recovery ( 1 ) when the light on the scene is assumed to be known and (2) when the light on the scene is unknown....
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...Substituting Eqs. (2) and (3) into Eq. ( 1 ) permits us to express the relationship between the daylight surface reflectances and sensor responses by the matrix equation px = A cx (4)...
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TL;DR: A new hypothesis for color constancy namely the gray-edge hypothesis, which assumes that the average edge difference in a scene is achromatic is proposed, and an algorithm forcolor constancy is proposed based on the derivative structure of images.
Abstract: Color constancy is the ability to measure colors of objects independent of the color of the light source. A well-known color constancy method is based on the gray-world assumption which assumes that the average reflectance of surfaces in the world is achromatic. In this paper, we propose a new hypothesis for color constancy namely the gray-edge hypothesis, which assumes that the average edge difference in a scene is achromatic. Based on this hypothesis, we propose an algorithm for color constancy. Contrary to existing color constancy algorithms, which are computed from the zero-order structure of images, our method is based on the derivative structure of images. Furthermore, we propose a framework which unifies a variety of known (gray-world, max-RGB, Minkowski norm) and the newly proposed gray-edge and higher order gray-edge algorithms. The quality of the various instantiations of the framework is tested and compared to the state-of-the-art color constancy methods on two large data sets of images recording objects under a large number of different light sources. The experiments show that the proposed color constancy algorithms obtain comparable results as the state-of-the-art color constancy methods with the merit of being computationally more efficient.
801 citations
Cites background or methods from "A spatial processor model for objec..."
...901808 after which the image is corrected [8]–[11], or they directly estimate the color corrected image [1], [12], after which the light source can be derived....
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...Buchsbaum [8] proposes the gray-world hypothesis which assumes that the average reflectance in a scene is achromatic....
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...Buchsbaum [8], for example, needed to make further assumptions on the basis functions for the camera sensitivities, the surface reflectances, and the light source spectra....
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...Another well-known simple color constancy method is based on the gray-world hypothesis [8], which assumes that the average reflectance in the scene is achromatic....
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Book•
03 Jan 1992
TL;DR: In this paper, the authors analyze two large sets of empirical surface spectral reflectances and examine three conjectures concerning constraints on surface reflectance: that empirical surface reflectances fall within a linear model with a small number of parameters, that empirical surfaces reflectances are within a matrix-based model composed of band-limited functions with only three or four parameters, and that the shape of the spectral-sensitivity curves of human vision enhances the fit between empirical surface reflectsances and linear models.
Abstract: Recent computational models of color vision demonstrate that it is possible to achieve exact color constancy over a limited range of lights and surfaces described by linear models. The success of these computational models hinges on whether any sizable range of surface spectral reflectances can be described by a linear model with about three parameters. In the first part of this paper, I analyze two large sets of empirical surface spectral reflectances and examine three conjectures concerning constraints on surface reflectance: that empirical surface reflectances fall within a linear model with a small number of parameters, that empirical surface reflectances fall within a linear model composed of band-limited functions with a small number of parameters, and that the shape of the spectral-sensitivity curves of human vision enhance the fit between empirical surface reflectances and a linear model. I conclude that the first and second conjectures hold for the two sets of spectral reflectances analyzed but that the number of parameters required to model the spectral reflectances is five to seven, not three. A reanalysis of the empirical data that takes human visual sensitivity into account gives more promising results. The linear models derived provide excellent fits to the data with as few as three or four parameters, confirming the third conjecture. The results suggest that constraints on possible surface-reflectance functions and the "filtering" properties of the shapes of the spectral-sensitivity curves of photoreceptors can both contribute to color constancy. In the last part of the paper I derive the relation between the number of photoreceptor classes present in vision and the "filtering" properties of each class. The results of this analysis reverse a conclusion reached by Barlow: the "filtering" properties of human photoreceptors are consistent with a trichromatic visual system that is color constant.
713 citations
References
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2,122 citations
Book•
01 Dec 1962
TL;DR: A composite thin film resistor is disclosed, including an electrically inert substrate upon which is deposited a nickel-chromium alloy thin film, and an overlying second thin film - which is initially deposited as metallic tantalum - which provides a very high degree of environmental protection with respect to the Ni-Cr film.
Abstract: A composite thin film resistor is disclosed, including an electrically inert substrate upon which is deposited a nickel-chromium alloy thin film, and an overlying second thin film - which is initially deposited as metallic tantalum. In the final product the tantalum is passivated, as by thermal oxidation, so that the said film is substantially tantalum oxide throughout, except where such film underlies a pair of conductive terminal pads. The terminal pads are spaced on the substrate, so that the resistive path therebetween is defined through the nickel-chromium thin film - via the thin metallic tantalum film interfacing between the nickel-chromium film and conductive pads. The overlying tantalum oxide provides a very high degree of environmental protection with respect to the Ni-Cr film, whereby the product not only displays the desirably low TCR characteristics of Ni-Cr, but is also highly resistant to moisture and other environmental factors. The product also exhibits outstanding resistance to the adverse effects of electrolysis supported by the presence of moisture. The various films, including a gold film from which the terminal pads are derived, may be deposited upon the inert substrate by sequential sputtering during a single evacuation of a vacuum chamber. Desired resistive patterns may then be formed by photo-etching, subsequent to which oxidation of accessible portions of the tantalum film can be effected by heating in an appropriate atmosphere.
1,683 citations
01 Jul 1972
TL;DR: A specific relationship between some of the current knowledge and thought concerning human vision and the problem of controlling subjective distortion in processed images are reviewed.
Abstract: A specific relationship between some of the current knowledge and thought concerning human vision and the problem of controlling subjective distortion in processed images are reviewed.
548 citations
455 citations
TL;DR: The perceived shade of gray depends primarily on the luminance relationship between surfaces percieved to lie in the same plane and not between surfaces that are merely adjacent in the retinal image, implying that depth perception must precede lightness perception and that lateral inhibition cannot explain lightness constancy.
Abstract: The perceived shade of gray depends primarily on the luminance relationship between surfaces percieved to lie in the same plane and not between surfaces that are merely adjacent in the retinal image This result implies that depth perception must precede lightness perception and that lateral inhibition cannot explain lightness constancy
443 citations