Fast JPEG image retrieval using optimised Huffman tables

With image databases expanding rapidly, fast retrieval solutions are highly sought after. Since most images are compressed in JPEG format, compressed-domain retrieval algorithms based on DCT coefficients can be employed to speed up feature extraction and comparison during retrieval. However, this approach is limited as the complete image files need to be read and partially decoded to obtain the required coefficient data. In this paper, we present a very fast method for retrieving JPEG compressed images. Our method is based on the Huffman tables contained in the JPEG header which can be optimised on a per image basis not only to improve compression rates but also to provide a very useful image descriptor. We show that feature extraction and comparison based on optimised Huffman tables takes only a fraction of the time compared to common image retrieval algorithm while resulting only in a relatively small drop in terms of retrieval accuracy.