Color Image Compression Using Fast VQ with DCT Based Block Indexing Method

In this paper, a Vector Quantization compression scheme based on block indexing is proposed to compress true color images. This scheme uses affine transform to represent the blocks of the image in terms of the blocks of the code book. In this work a template image rich with high contrast areas is used as a codebook to approximately represent the blocks of the compressed image. A time reduction was achieved due to the usage of block descriptors to index the images blocks, these block descriptors are derived from the discrete cosine transform (DCT) coefficients. The DCT bases descriptor is affine transform invariant. This descriptor is used to filter out the domain blocks, and make matching only with similar indexed blocks. This introduced method led to time (1.13sec), PSNR (30.09), MSE (63.6) and compression ratio (7.31) for Lena image (256x256, 24bits).