Fast Arbitrary Resizing of Images in DCT Domain

Limited storage and bandwidth have long necessitated the use of images and videos in compressed formats. Resizing of images in compressed domains such as discrete cosine transform (DCT) are developed primarily to avoid the computation associated to decompression and compression for spatial techniques. An important application of this work is transcoding of image and video content to achieve reduction of spatial resolution. In this work, arbitrary resizing of images by factors of P/Q times R/S, where P, Q, R, and S are positive integers is considered. An efficient approach is derived by performing up-sampling and down-sampling simultaneously. All computations are carried out with N times N DCT blocks to simplify integration with block based coders such as JPEG and MPEG. Simulation results revealed that our proposed approach achieves significant reduction up to 50% of the computational cost and visually sharper images compared to existing methods.