FILTER ELIMINATING BLOCK NOISE IN COMPANDED IMAGE AND FILTER METHOD

摘要

PROBLEM TO BE SOLVED: To eliminate block shaped noise that is produced when an image whose high frequency component is lost by a high compression rate is decoded in decoding a still image by inverse discrete cosine transformation IDCT. SOLUTION: A block prevention filter used to prevent transposition of a block shaped noise in a moving image technology is adopted so as to check whether or not an edge at a border of blocks is natural in the vertical and horizontal directions and to apply filtering to the edge. In the case of the horizontal direction, for example, mean values of values of pixels P0 -P3 and pixels P4 -P7 are compared and the result indicates an exceeded threshold level, the filtering is applied to one or both of the P0 -P3 and pixels P4 -P7 so that the P0 -P7 are changed smoothly.