  The Block Transform Coded, JPEG- a lossy image compression format has been
used to keep storage and bandwidth requirements of digital image at practical
levels. However, JPEG compression schemes may exhibit unwanted image artifacts
to appear - such as the 'blocky' artifact found in smooth/monotone areas of an
image, caused by the coarse quantization of DCT coefficients. A number of image
filtering approaches have been analyzed in literature incorporating
value-averaging filters in order to smooth out the discontinuities that appear
across DCT block boundaries. Although some of these approaches are able to
decrease the severity of these unwanted artifacts to some extent, other
approaches have certain limitations that cause excessive blurring to
high-contrast edges in the image. The image deblocking algorithm presented in
this paper aims to filter the blocked boundaries. This is accomplished by
employing smoothening, detection of blocked edges and then filtering the
difference between the pixels containing the blocked edge. The deblocking
algorithm presented has been successful in reducing blocky artifacts in an
image and therefore increases the subjective as well as objective quality of
the reconstructed image.
