.[.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 an embodiment, the filtering unit
is configured to select a filtering mask 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 filtering unit is configured to perform
at least one comparison, and the comparison compares a determined value
and a threshold. The determined value is based on the pixel to be
filtered and the at least one candidate pixel, and the threshold is based
on quantization information of at least a portion of the image including
the pixel to be filtered. .Iaddend.