Global image enhancement in the DCT domain

The JPEG that applies discrete cosine transform (DCT) is one of the most popular image compression methods. Enhancement in the compressed domain offers two major advantages, including low computational complexity and storage space. To enhance an image in compression domain, the main issue is to develop an effective technique that limits the introduction of blocking artifacts. In this paper, we propose a new merging strategy to generate global DCT-like matrix, which achieve not only global enhancement but removing block artifacts in compressed-domain. In addition, we also propose multi-enhancement factors based on the distribution of frequency for fine tune image enhancement. From the simulation results, the proposed method provides an effective improvement for image enhancement and significant reduction in the introduction of block artifacts.