Fast DCT domain image shifting and merging

In high-speed color image processing applications, the manipulation of DCT domain images in real time is often required. Because of throughput requirements, operations necessary for the building of a printer page, such as merging and shifting, cannot be performed in the sampled domain since the overhead associated with the DCT slows computation. In this paper we present an efficient method for the merging or shifting of JPEG-compressed images, performed in the DCT domain to avoid additional overhead. The algorithm exploits quantization to achieve further gains. The resulting algorithm can save between 25 % and 75 % of the required operation cycles in a typical image processing system.