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Block noise level evaluation method for compressed images and control method of imaging device utilizing the evaluation method

  • US 20060034531A1
  • Filed: 05/10/2005
  • Published: 02/16/2006
  • Est. Priority Date: 05/10/2004
  • Status: Abandoned Application
First Claim
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1. A block noise level evaluation method that evaluates a level of potential block noise arising on each block boundary in a compressed image, which is obtained by compression subsequent to division of an original image into multiple blocks of a preset number of pixels both in a horizontal direction and in a vertical direction, said block noise level evaluation method comprising the steps of:

  • (a) calculating a luminance variation at each target pixel in the compressed image from luminance values of the target pixel and of an adjacent pixel adjoining to the target pixel in a preset direction;

    (b) computing a smoothness degree of luminance variation at the target pixel from an anterior difference between the calculated luminance variations at the target pixel and an anterior pixel adjoining to the target pixel in the preset direction and a posterior difference between the calculated luminance variations at the target pixel and a posterior pixel adjoining to the target pixel in the preset direction;

    (c) computing a block noise evaluation index from a specific ratio of an average smoothness degree of luminance variation for boundary pixels located on the block boundary to an average smoothness degree of luminance variation for inner pixels not located on the block boundary; and

    (d) evaluating the level of potential block noise corresponding to the computed block noise evaluation index.

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