Image extraction in DCT domain

More and more digital images are being stored in compressed formats, among which the format using discrete cosine transform (DCT) coefficients is widely adopted (JPEG, MPEG, H.263 etc). To exploit those successful image processing techniques developed in the pixel domain, the authors propose a fast image extraction algorithm to allow images to be extracted directly from compressed DCT coefficients without full decompression. In the proposed technique the extracted images retain quality comparable with that of fully decoded images. However, the computing cost and the storage expense incurred by the proposed algorithm are very much lower than the costs of full decompression. The experiments also demonstrate that the proposed algorithm has tremendous potential in that all existing image processing techniques developed in the pixel domain can be directly applied to compressed images, without involving full decompression.