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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Proceedings ArticleDOI
Image Enhancement Using a Contrast measure in the Discrete Wavelet Transform
TL;DR: A new image enhancement technique based on a proposed contrast measure in the discrete wavelet transform is proposed that has better visual quality when compared with previous discrete cosine transform- based enhancement technique.
Dissertation
Élaboration d'une technique de tatouage vidéo basée sur la perturbation des vecteurs de mouvement
TL;DR: In this article, the authors propose a solution for the protection of contenus video, based on a perturbation of the vecteurs de mouvement.
Proceedings ArticleDOI
Activity based Contrast Enhancement of Compressed Digital images in DCT Domain
TL;DR: Subjective and objective tests validate the concept of activity based contrast enhancement and the avoidance of block artifacts in the resultant image.
Proceedings ArticleDOI
Local contrast stretch based tone mapping for high dynamic range images
TL;DR: The method is fast and easy to use, and the experiment results show that the technique can produce good results on a variety of high dynamic range images.
Journal ArticleDOI
Design and validation of an attention model of web page users
Ananya Jana,Samit Bhattacharya +1 more
TL;DR: A model to predict the locations of the most attended pictorial information on a web page and the attention sequence of the information, which takes into account three characteristics of an image object: chromatic contrast, size, and position and computes a numerical value, the attention factor.
References
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Journal ArticleDOI
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.