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.