Blocking artifacts are the major coding artifacts caused by
high compression. These appear as grid noise along the block
boundaries in smooth areas and are caused due to independent
encoding of each block without considering the correlation
between adjacent blocks. To reduce irrelevancy, redundancy
of the image data and volume of data to be transmitted, image
compression is must. However with the use of lossy image
compression methods blocking artifacts get introduced. A
compression artifact is a noticeable distortion of media which
may be an image, audio or video, due to the application of an
overly aggressive or inappropriate lossy data compression
algorithm. These lossy data compression schemes discard
some data to simplify the media sufficiently to store it in the
desired space (data-rate). If there is not enough data in the
compressed version to reproduce the original with acceptable
fidelity, artifacts will result. Alternatively, the compression
algorithm may incorrectly determine certain distortions to be
of little subjective importance but they may in fact be
objectionable to the viewer. The artifacts such as over
smoothing of images, degradation due to quantization errors,
ringing effects, blurring of images, blocking noise, image
features irregularities etc. So to overcome these artifacts,
various methods are used such as Normal DCT filtering,
Spatial Filtering, Hybrid Filtering methods, DWT, Adaptive
Fuzzy Filtering method, iterative reconstruction algorithm etc.
The boundary regions between blocks are identified as either
smooth or non-smooth regions [2]. The blocking artifacts in
smooth regions are removed by modifying a few DCT
coefficients appropriately, whilst an edge-preserving
smoothing filter is applied to the non-smooth regions. Above
mentioned algorithms are highly efficient in removing
blocking artifacts and produce visuality that is much more
pleasing to the eye.