Image retrieval using local compact DCT-based represention

An image retrieval system based on local affine frames is introduced. The system provides highly discriminative retrieval of rigid objects under a very wide range of viewing and illumination conditions, and is robust to occlusion and background clutter. Distinguished regions of data dependent shape are detected, and local affine frames (coordinate systems) are obtained. Photometrically and geometrically normalised image patches are extracted and used for matching. Local correspondences are formed either by direct comparison of photometrically normalised colour intensities in the normalised patches, or by comparison of DCT (discrete cosine transform) coefficients of the patches. Experimental results are presented on a publicly available database of real outdoor images of buildings. We demonstrate the effect of the number of DCT coefficients that are used for the matching. Using the DCT, excellent results with a retrieval performance of 100% in rank 1 are achieved, and memory usage is reduced by a factor of 4.