Classified JPEG coding of mixed document images for printing

This paper presents a modified JPEG coder that is applied to the compressio n of mixed documents (containing test, natural images, and graphics) for pr inting purposes. The modified JPEG; coder proposed in this paper takes adva ntage of the distinct perceptually significant regions in these documents t o achieve higher perceptual quality than the standard JPEG coder. The regio n-adaptivity. is performed via classified thresholding being totally compli ant with the baseline standard. ii computationally efficient classification algorithm is presented, and the improved performance of the classified JPE G coder is verified.