A VQ/DCT coding scheme for colour images

A VQ/DCT (vector quantization/discrete cosine transform) coding scheme for color images is examined. In this coding scheme, VQ is first employed to code a 24-bits/pixel color image, which is composed of three components, R, G, B, into an 8-bits/pixel index image. Then the DCT is applied to the index image. One major problem in this coding scheme is that the codebook produced by the VQ process is randomly arranged. Using this codebook to VQ-code color images destroys the correlation present in the original images. Some techniques for producing a codebook which retains a reasonable degree of correlation are proposed