Transmission of the color information using quad-trees and segmentation-based approaches for the compression of color images with limited palette

The compression of color images is usually performed independently along each of the 3 axis of a luminance-chrominance color space. When applied to images using a limited color palette, it generates images which take on more values than those found in the original color palette. These images must be color quantized before they can be displayed with a limited palette. In this paper, we present two new approaches for the lossy compression of color quantized images that does not require color quantization of the decoded images. The algorithms restrict the pixels of the decoded image to take values only in the original color palette. The first algorithm does so by using lists of colors taken by pixels in variable block sizes. The second one uses a color segmentation of the image. These two approaches improve the performance of previously proposed algorithms. For comparable quality and similar bit rate, the proposed approaches have lower decoding complexity than standard DCT-based coding algorithms