The reconstructed images after compression produce annoying blocking
artifacts near block boundaries, particularly in a low bit-rate image
compression, because each block is transformed and quantized
independently. Detection of blocking artifact has an important role in the
design of image coding systems. Increasing the bit rate to obtain better
quality images is too costly. In this paper, a novel pixel-domain
technique for image blocking artifact detection is presented. The
algorithm detects the regions of the image which present visible blocking
artifacts. The blocking artifact detection and reduction are presented as
a post- processing in the image decoder. The algorithm first detects the
direction of the artifact through power spectrum estimation of the pixel
absolute difference (PAD) in both horizontal and vertical directions. The
power spectrum of the PAD is estimated using the Maximum Entropy
method (MEM) which is a nonparametric method to perform accurate
power spectrum estimation. The reduction process is applied only on the
direction of artifacts to improve the image quality. The key of the
reduction process is based on the modified-projection operator to give
reasonable modifications for the block boundary pixels. The simulation
results illustrate the performance of the proposed method for the JPEG
decoded images.