Journal ArticleDOI
Contrast in complex images.
TLDR
A definition of local band-limited contrast in images is proposed that assigns a contrast value to every point in the image as a function of the spatial frequency band and is helpful in understanding the effects of image-processing algorithms on the perceived contrast.Abstract:
The physical contrast of simple images such as sinusoidal gratings or a single patch of light on a uniform background is well defined and agrees with the perceived contrast, but this is not so for complex images. Most definitions assign a single contrast value to the whole image, but perceived contrast may vary greatly across the image. Human contrast sensitivity is a function of spatial frequency; therefore the spatial frequency content of an image should be considered in the definition of contrast. In this paper a definition of local band-limited contrast in images is proposed that assigns a contrast value to every point in the image as a function of the spatial frequency band. For each frequency band, the contrast is defined as the ratio of the bandpass-filtered image at the frequency to the low-pass image filtered to an octave below the same frequency (local luminance mean). This definition raises important implications regarding the perception of contrast in complex images and is helpful in understanding the effects of image-processing algorithms on the perceived contrast. A pyramidal image-contrast structure based on this definition is useful in simulating nonlinear, threshold characteristics of spatial vision in both normal observers and the visually impaired.read more
Citations
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Journal ArticleDOI
Ramp Distribution-Based Contrast Enhancement Techniques and Over-Contrast Measure
Seung Youn Lee,Changick Kim +1 more
TL;DR: This paper shows that the average intensity distribution of natural images can be linearly approximated to the ramp distribution in an ordered histogram domain as the contrast increases, and proposes ramp distribution-based global and local CE algorithms.
Journal ArticleDOI
Toward a unified fidelity metric of still-coded images
TL;DR: This work has performed an individual evaluation of the main visual model components in order to propose a unified fidelity metric with low complexity and high performance for frequency selectivity of human vision, perceived contrast, masking effects, pooling, and visual attention.
Proceedings ArticleDOI
A computational model for perception of stereoscopic window violations
TL;DR: This paper investigates stereoscopic window violation artifacts, which often interfere with artistic freedom and constrain the comfortable depth volume, and presents a model predicting problematic window violations that are visually disturbing.
Journal ArticleDOI
Rendering a virtual light source to seem like a realistic light source in an electronic display: A critical band of luminance gradients for the perception of self-luminosity
TL;DR: The quantitative rule governing the perception of self-luminosity is investigated and applied to improve the fidelity of light sources in virtual environments and the gradients around the peak of the critical band won the highest rating of perceptual fidelity.
Image quality assessment based on a human visual system model
TL;DR: In this article, the authors propose a method to improve the quality of the data collected by the data collection system of the National Archives of the United States, which is used for data collection.
References
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Chapter 9 Visual adaptation and retinal gain controls
Journal ArticleDOI
Feature Detection in Human Vision: A Phase-Dependent Energy Model
TL;DR: A simple and biologically plausible model of how mammalian visual systems could detect and identify features in an image is presented and it is suggested that the points in a waveform that have unique perceptual significance as ‘lines’ and ‘edges’ are the points where the Fourier components of the waveform come into phase with each other.
Journal ArticleDOI
Contrast constancy: deblurring in human vision by spatial frequency channels.
Mark A. Georgeson,G.D. Sullivan +1 more
TL;DR: It is argued that spatial frequency channels in the visual cortex are organized to compensate for earlier attenuation, and achieves a dramatic 'deblurring' of the image, and optimizes the clarity of vision.