Fast DCT-domain image shifting and merging

In high-speed color image processing applications, it is desired to manipulate DCT-domain images in real time. Because of throughput requirements, operations required for the building of a printer page, such as merging and shifting, cannot be performed in the sampled domain - 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.