Pointwise Shape-adaptive Dct Denoisingwith Structure Preservation in Luminance-chrominance Space

The shape-adaptive DCT (SA-DCT) [12, 13] is a low-complexity transform which can be computed on a support of arbitrary shape. Particularly suited for coding image patches in the vicinity of edges, the SA-DCT has been included in the MPEG-4 standard [7]. The use of this shape-adaptive transform for grayscale image denoising has been recently proposed [3, 2], showing a remarkable performance. In this paper we extend this approach to color Þltering in luminance-chrominance space, exploiting the structural information obtained from the luminance channel to drive the shape-adaptation for the chrominance channels. Several simulation experiments attest the advanced performance of the proposed color denoising method. The visual quality of the estimates is high, with sharp detail preservation, clean edges, and without unpleasant ringing artifacts introduced by the Þtted transform. Besides noise removal, the proposed method is also effective in dealing with those artifacts which are often encountered in compressed images and videos. Blocking artifacts are suppressed while salient image features are preserved. The SA-DCT Þltering used for the chrominance channels allows to faithfully reconstruct the missing structural information of the chrominances, thus correcting colorbleeding artifacts. Being based on the SA-DCT (which is implemented as standard in modern MPEG hardware), the proposed method can be integrated within existing video platforms as a preor post-processing Þlter.