Image postprocessing by Non-local Kuan's filter

  • Authors:

  • Renqi Zhang;Wanli Ouyang;Wai-Kuen Cham

  • Affiliations:

  • Department of Electronic Engineering, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong;Department of Electronic Engineering, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong;Department of Electronic Engineering, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong

  • Venue:
  • Journal of Visual Communication and Image Representation
  • Year:
  • 2011

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Abstract

Blocking artifacts exist in images and video sequences compressed to low bit rates using block-based discrete cosine transform (DCT) compression standards. In order to reduce blocking artifacts, two image postprocessing techniques, DNLK filter and OCDNLK filter, are presented in this paper. A more accurate DCT domain Kuan's filter based on Non-local parameter estimation was proposed from the linear minimum mean-square-error (MMSE) criterion. We analyze the required two assumptions for the filter theoretically. Then the DCT domain Kuan's filter for low frequency coefficients and Non-local mean filter for high frequency AC coefficients constitute the proposed Non-local Kuan's (NLK) filter. After that, we propose the Dual Non-local Kuan's (DNLK) filter by applying the proposed filter in dual layer. The DNLK filter is extended to form the Overcomplete Dual Non-local Kuan's (OCDNLK) filter by applying to the overcomplete DCT coefficients. Experimental results on coded images using test quantization tables and JPEG coded images show the effectiveness of the two methods.