Image signal processing.

摘要

A technique is provided for processing a decoded image signal (S10) having distortion and obtained by decoding coded data by utilizing a two-dimensional inverse orthogonal transformation, the coded data having been obtained by coding an image signal by utilizing a two-dimensional orthogonal transformation. The technique constructs (10) at least one correction block each including a plurality of pixels from a plurality of coded blocks from the decoded image signal and having a distortion on at least one boundary therebetween. The coded blocks of each correction block are adjacent to one another. A two-dimensional orthogonal transformation of each correction block is performed (11) by utilizing a Haar function so as to form coefficients including higher-order side coefficients (404), lower-order side coefficients (403) and a dc coefficient (402). A correction value is added to the higher-order side coefficients in accordance with a predetermined number of the lower-order side coefficients when the predetermined number of the lower-order side coefficients has values other than zero so as to form a correction coefficient signal for each correction block. A two-dimensional inverse orthogonal transformation (15) is performed on the correction coefficient signal of each correction block by utilizing the Haar function so as to obtain a smoothed image signal in which each distortion on each boundary of the coded blocks has been smoothed.