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Authors
Affiliations
1 Computing Department, Federal University of Ouro Preto, Ouro Preto, BR
2 Equipe A3SI, ESIEE Paris, Universite Paris-Est, Noisy-le-Grand, FR
3 PPGIA, Pontificia Universidade Catolica do Parana, Curitiba, BR
4 Computing Department, Universidade Federal de Minas Gerais, Belo Horizonte, BR
Source
AIRCC's International Journal of Computer Science and Information Technology, Vol 4, No 5 (2012), Pagination: 243-259
Abstract
In this work, we formalize a generic fast hue-preserving histogram equalization method based on the RGB color space for image contrast enhancement and two versions of that generic process. The first method estimates a RGB 3D histogram to be equalized using R-red, G-green, and B-blue 1D histograms, while the second method employs RG, RB, and GB 2D histograms. The histogram equalization is performed using shift hue-preserving transformations, avoiding unrealistic colors. Our methods have linear time and space complexities with respect to the size of the image and do not need to apply conversions from a color space to another in order to perform the image enhancement. Such design complies with real-time applications requirements. An objective assessment comparing our methods and others is performed using a contrast measure and a color image quality measure, where the quality is established as a weighting of the naturalness and colorfulness indexes. We analyze 300 images from the dataset of the University of Berkeley. Experiments show that the value of the image contrast produced by our methods is in average 50% greater than the original image value, keeping the quality of the produced images close to the original one.
Keywords
Histogram Equalization, Contrast Enhancement, Hue-Preserving, Color Image, RGB Color Space.
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