.[.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 filtering mask is
selected based on a position of a pixel to be filtered. The filtering
mask includes the pixel to be filtered and at least one candidate pixel.
The pixel to be filtered is filtered by applying a weighted averaging
operation to the pixel to be filtered and the at least one candidate
pixel. The weighted averaging operation includes applying weight to at
least one of the pixel to be filtered and the at least one candidate
pixel in producing a weighted sum value, and performing a shift operation
on the weighted sum value to divide by a desired value..Iaddend.