An image compression algorithm using warped discrete cosine transform

This paper introduces the concept of warped discrete cosine transform (WDCT) and an image compression algorithm based on the WDCT. The proposed WDCT is a cascade connection of a conventional DCT and all-pass filters whose parameters can be adjusted to provide frequency warping. In the proposed image compression scheme, the frequency response of the all-pass filter is controlled by a set of parameters with each parameter for a specified frequency range. For each image block, the best parameter is chosen from the set and is sent to the decoder as a side information along with the result of corresponding WDCT coefficients. It is shown that the WDCT can be implemented by a single matrix computation like the DCT. The proposed algorithm outperforms the DCT based compression, for high bit rate applications and for images with high frequency components.