Processing JPEG-compressed images and documents

As the Joint Photographic Experts Group (JPEG) has become an international standard for image compression, we present techniques that allow the processing of an image in the “JPEG-compressed” domain. The goal is to reduce memory requirements while increasing speed by avoiding decompression and space domain operations. In each case, an effort is made to implement the minimum number of JPEG basic operations. Techniques are presented for scaling, previewing, rotating, mirroring, cropping, recompressing, and segmenting JPEG-compressed data. While most of the results apply to any image, we focus on scanned documents as our primary image source.