Variable compression using JPEG

To meet various transmission and storage constraints, it is desirable that a compression algorithm allows a range of compression ratios. In this paper we analyze the JPEG compression algorithm, the international standard for compressing continuous tone images, and show how higher compression ratios can be achieved with minimal loss in image quality. We compare three methods to achieve variable compression with JPEG. Through a comprehensive analysis using 8 standard monochrome images from the USC database, we propose a method that offers substantial visual quality advantages for high compression ratios. The comparisons have been made by using an objective distortion measure which corresponds well to subjective assessments of visual quality. The paper provides detailed motivation for the algorithms, and suggests the choice of parameters to obtain variable compression with minimal loss in visual quality