METHOD AND APPARATUS FOR PROCESSING BLOCK CODED IMAGE DATA TO REDUCE BOUNDARY ARTIFACTS BETWEEN ADJACENT IMAGE BLOCKS

A method and apparatus for processing block coded image data wherein each block comprises a plurality of pixels. A local pixel is selected from a first block of pixels. The selected pixel is preferably near a border between the first block of pixels and a second block of pixels. At least one external pixel is selected from the second block of pixels. The selected external pixel(s) is (are) also near the border. The selected local pixel is modified to reduce the difference between the local pixel and the selected external pixel(s). The selected pixel value is modified as follows. A low pass filter coefficient is selected for each selected local pixel value and for each selected external pixel value. The selected local pixel value and the external pixel values are each multiplied by their corresponding low pass filter coefficient. The products of these multiplications are summed together to form a low pass filtered pixel value.