Abstract: In many applications, image resizing is needed to change the scale of digital images. Resizing of a compressed image can be performed in a spatial domain. However, the performance will be much faster when in a compressed domain. In this work, an algorithm for arbitrarily resizing images in DCT domain based on the distributive property of unitary transformation to matrix multiplication is advanced and the relationship between blocks and sub-blocks is addressed. This algorithm has higher PSNR and lower computation costs than the conventional ones and is applicable to both intracoding frames and intercoding frames. When combined with motion compensation algorithm in DCT domain, it can achieve real time video transcoding.