No-reference noticeable blockiness estimation in images

Blocking artifact is a prevailing degradation caused by the block-based Discrete Cosine Transform (BDCT) coding technique under low bit-rate conditions. In this paper, we propose an efficient no-reference noticeable blockiness estimation algorithm for BDCT coded images. The difference on block boundaries is first measured and then transformed into the block discontinuity map. We consider the effects of luminance adaptation and texture masking on blocking and integrate them using a nonlinear operator to form an overall masking map. This map is finally incorporated with the discontinuity map to generate Noticeable Blockiness Map (NBM), which can be used to guide perceptual quality assessment, codec parameter optimization, post-processing, etc. We have demonstrated the validity of the NBM through its applications in no-reference image quality assessment and image deblocking.