Enhancement of MPEG/JPEG images based on histogram equalization without gamut problem
Akira Taguchi · 2008
In the case of digital image/video processing, color images are represented in the YCbCr. The Y component is the luminance of the color. The other two components Cb,Crrepresent the color-difference component. The bandwidth of Cb,Crcomponents are much smaller than that of luminance signal. Thus, this color space is suitable for image compression and adopted for JPEG and MPEG. The YCbCrcolor space is related with the HSI (hue, saturation, intensity) color space. The HSI color space is an ideal tool for developing image processing. In this paper, we propose a novel method which is combined the luminance enhancement and the saturation enhancement, in the YCbCrcolor space. The width and shape of (Cb,Cr) space is changed depending on the value of Y component. Since, the saturation enhancement method must be given limiting condition for the RGB color space, the constrained condition for the values of Cb,Crare derived. Thus, the proposed method is free from gamut problem.