Abstract : (IEEE Trans. on Image Processing, vol. 12, no.12, pp. 1591-1598, December, 2003. See IEEE Copyright Notice)
The first step in many
techniques for processing intensity and saturation in color images keeping hue unaltered,
is to transform the image data from RGB space to other color spaces such as LHS, HSI, YIQ,
HSV etc. Transforming from one space to another and processing in these spaces generate
gamut problem, i.e., the values of the variables may not be in their respective intervals.
Enhancement techniques for color images are studied here in a generalized setup. A
principle is suggested to make the transformations gamut problem free in this regard.
Using the same principle a class of hue preserving contrast enhancement transformations
are proposed, which generalize the existing gray level contrast intensification
techniques to color images. These transformations are also seen to bypass the above
mentioned color co-ordinate transformations for image enhancement. The developed principle
is used to generalize the histogram equalization scheme for gray scale images to
color images.
Results :
Original Images
Linearly Enhanced Images (proposed method)
Enhanced Images using S-type function(proposed method)
Enhanced Images using Histogram Equalization(proposed method)
Enhanced Images using Yang et al's Method(effect of saturation clipping can be seen in the artificial image with color boxes)
Enhanced Images using Weeks et al's Method
