.[.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..]. .Iadd.In the method, a pixel of an image is
filtered according to a filtering methodology. The filtering methodology
includes selecting at least one candidate pixel to be associated with an
averaging operation, and comparing a difference between the pixel to be
filtered and the candidate pixel with a threshold. The filtering
methodology further includes performing the averaging operation with
respect to the pixel to be filtered based on the candidate pixel if the
threshold is greater than the difference..Iaddend.