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A New Spatio-Chromatic Transform for Improved Lossy Coding of Color Images
by
Irina Popovici
United States Naval Academy
Coauthors: W. D. Withers
We introduce the eidochromatic transform as a tool for improved lossy coding of color images. Many current image-coding formats (such as JPEG 2000) utilize both a color-component transform (relating values of different image components at a single location) and a wavelet or other spatial transform (relating values of a single image component at proximate, but different image locations). Our eidochromatic transform further reduces redundancy by relating image values simultaneously across color components and in the two spatial dimensions. It uses the wavelet-transformed luminance plane, L, to transform the wavelet-transformed chrominance planes, Cr and Cb, based on a redundancy principle that luminance coefficients and chrominance coefficients tend to be small together in the smooth areas of the image, or large together near edges or other structure in the image.
The eidochromatic operator T consists of a pair of operators TS and TE that decompose chrominance vectors in components locally parallel and perpendicular to luminance, respectively. These local rotations are applied recursively to the resulting S-coefficients, in a merging progression that allows for preservation of the spatial scalability of data.
In tests, the eidochromatic operator reduced the overall static entropy of the chrominance components of quantized transformed images by up to 40% or more. Combined with JPEG 2000's modeling and coding method, the eidochromatic transform was found to reduce the size of lossily coded color images by up to 17% overall.
Date received: December 9, 2003
Copyright © 2003 by the author(s). The author(s) of this document and the organizers of the conference have granted their consent to include this abstract in Atlas Conferences Inc. Document # cakt-11.