Dominant colour extraction in DCT domain

As most of MPEG and JPEG compression standards are DCT-based, we propose a simple, low-cost and fast algorithm to extract dominant colour features directly in DCT domain without involving full decompression to access the pixel data. As dominant colour is one of the colour features used in constructing MPEG-7 dominant colour descriptors, the proposed algorithm would provide useful technique for those already compressed videos and images, where MPEG-7 dominant colour descriptors are needed. While the proposed algorithm presents advantages in terms of computing efficiency, i.e. eliminating the need of IDCT for compressed videos and images, extensive experiments also support that the proposed algorithm achieves competitive performances in extracting dominant colour features when compared with the pixel domain extraction described in MPEG-7.