3-D histogram modification of color images

While histogram modification has traditionally been used for the enhancement of color images, it has usually been restricted to processing the luminance component and, in some cases, the saturation. Reducing the problem's dimensionality in this manner generally sacrifices the ability to make full use of the color space gamut. Presented here are two novel color image contrast enhancement approaches which operate in three dimensions and aim for full gamut utilization. One is an extension of the histogram explosion algorithm to operate in CIELUV color space, intended to produce perceptually improved results compared to the original RGB method. The other is a new and very efficient recursive method, 'histogram decimation,' whose output is roughly similar to that of the RGB histogram explosion algorithm. Both algorithms are briefly discussed along with their major characteristics. A direct comparison follows, based on processing a set of standard test images. The performance analysis quantitatively compares the computation time and the mean-squared error in the cdf vs. an ideal, uniform distribution.