Method of filtering an image based on comparisons

摘要

A method and apparatus to remove a block effect and a ring effect appearing in a compression-coded image is disclosed. The present invention is especially applicable to an image compression-coded at a low bit rate. In particular, the present invention includes a variety of masks for the removal of the block/ring effect. Thus, one mask is select for a pixel to be filtered. Moreover, candidate pixels to be averaged with the pixel to be filtered is selected from the pixels of the selected mask to better maintain the details of the image, and a weight is applied to improve the calculation speed of the averaging operation. More particularly, the masks according to the present invention have longer tabs toward adjacent blocks at boundaries of the given block to remove the block and ring effect. In the method, a pixel of an image is filtered according to a filtering methodology. The filtering methodology includes more than one comparison, and each comparison compares a respective determined value and a respective threshold. Each respective determined value may be based on a respective difference value, and each respective difference value may be based on a different difference. At least one the difference values may be based on the pixel being filtered and another pixel.