Fast image resizing in discrete cosine transform domain with spatial relationship between DCT block and its sub-blocks

This paper presents a computational scalable approach to resize images by factors of P/Q times R/S in the discrete cosine transform (DCT) domain. Our resizing approach is based on the framework proposed by Mukherjee and Mitra which employs the spatial relationship between a DCT block and its sub-blocks. To simplify integration with block based coders such as JPEG and MPEG, N times N DCT blocks are discussed throughout this work. Our observation of the spatial relationship between a DCT block and its sub-blocks resulted in reduction of the computational cost to resize images. Also, we have suggested using up-sampled DCT blocks smaller than N times N to further reduce computational cost.