A simple algorithm for image retargeting in the compressed domain is proposed. Most existing retargeting algorithms work directly in the spatial domain of the raw image. Here, we work on the DCT coefficients of a JPEG-compressed image to generate a gradient map that serves as an importance map to help identify those parts in the image that need to be retained during the retargeting process. Each 8 × 8 block of DCT coefficients is scaled based on the least importance value. Retargeting can be done both in the horizontal and vertical directions with the same framework. We also illustrate image enlargement using the same method. Experimental results show that the proposed algorithm produces less distortion in the retargeted image compared to some other algorithms reported recently.
Dr. Oruganti Venkata Ramana Murthy, Muthuswamy, K., Rajan, D., and Tien, C. L., “Image Retargeting in Compressed Domain”, in 2010 20th International Conference on Pattern Recognition, 2010.