Dr. Jennifer Burg

Department of Computer Science

Research Project for Undergraduates

Indexed Color and Dithering for Digital Images

Indexed color is a color mode that reduces RGB color – which with three bytes per color offers more than 16 million colors – to a palette of 256 colors or fewer. This can be done by a number of methods, including popularity, uniform partitioning, median cut, and octree algorithms, among others. Photoshop’s indexed color mode allows the user to choose a perceptual, selective, or adaptive mode for the color reduction. These are based on properties of human perception and color combination. Dithering can be used in conjunction with indexed color to reduce some of the blockiness that results from a reduction of the palette. When one of the original colors is removed from the palette, it is simulated by painting neighboring pixels with available colors in a way that is blended by the eye. This project involves implementing a variety of indexed color algorithms along with dithering and comparing the results on different types of images. The researcher will investigate what is meant by Photoshop’s perceptual, selective, or adaptive options and will try to replicate these or propose new options in their implementations. For more information, see Section 3.3 in http://www.cs.wfu.edu/%7Eburg/nsf-due-0340969/textbased/Chapter3CS.pdf.