Image quality improvement by pre- and post-processing in DCT coding

Coding for full-color still-image is standardized internationally by JPEG (Joint Photographic Experts Group). The coding method is used in wide area applications. In many cases, continuous-tone images are accompanied by characters. So improvements of JPEG coding by pre and post processing are investigated in mixed images. In this process, we use sharpening before JPEG coding as a pre-processing, and we use smoothing after JPEG coding as a post- processing. In both pre and post processing, the degree of emphasis is controlled by a weighting factor and the quality is compared between processed and unprocessed images. As a result of this process, it is confirmed that the processed image is better than an unprocessed image in quality.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.