Fast method for joint retrieval and identification of JPEG coded images based on DCT sign

We propose a fast method to retrieve images from a JPEG image database. The proposed method is intended to retrieve similar images, including their compressed versions, and to identify exact match and all compressed versions of a query image simultaneously. Similarity level is measured based on the non-zero DCT coefficients signs, which serve as features. The method is simple and fast because the DCT coefficients signs can be obtained by only entropy-decoding the bitstream. There is no need to calculate features explicitly. Furthermore, the method is robust to JPEG compression, particularly for image identification purpose.