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
A Critical Analysis on Perceptual Contrast and Its Use in Visual Information Analysis and Processing
Azeddine Beghdadi,Muhammad Ali Qureshi,Seyed Ali Amirshahi,Aladine Chetouani,Marius Pedersen +4 more
TL;DR: A critical review of contrast measures and associated models developed by the scientific community in vision, optics, and image processing is presented and learned lessons and guidelines on the use of appropriate contrast measures in selected visual information processing and analysis applications are provided.
Proceedings ArticleDOI
Human Computer Interaction: Legibility and Contrast
Zuffi,Brambilla,Beretta +2 more
Proceedings Article
Visual Differences In Colour Reproduction And Their Colorimetric Correlates.
Jan Morovic,Pei-Li Sun +1 more
TL;DR: A colorimetrically based metric that takes into account some aspects of the visual system and using information both about the statistics of colour differences, of the original images and of changes to spatial characteristics is able to give a close prediction of observer responses.
Journal ArticleDOI
Structured-illumination reflectance imaging for the detection of defects in fruit: Analysis of resolution, contrast and depth-resolving features
Yuzhen Lu,Renfu Lu +1 more
TL;DR: In this article, a set of experiments were performed on standard optical targets and apple samples by using illumination patterns over a wide range of spatial frequencies of 0.01-1.0 cycles mm−1 to examine the features of SIRI.
Proceedings ArticleDOI
Memetic algorithm based feature selection for hyperspectral images classification
TL;DR: A novel feature selection method for hyperspectral image classification is proposed, which is based on a newly designed memetic algorithm, which can obtain stable and superior feature subsets for classification.
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.