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Adaptive thresholder

  • US 4,468,704 A
  • Filed: 10/28/1982
  • Issued: 08/28/1984
  • Est. Priority Date: 10/28/1982
  • Status: Expired due to Fees
First Claim
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1. Apparatus for adaptively thresholding the image pixels that comprise a video image signal on a pixel by pixel basis to distinguish white and black image areas in said video image signal, comprising, in combination:

  • (a) white image signal parameter generating means responsive to transition of the video image signal from black to white to provide a white image signal parameter equal to larger of said video image signal and a preset minimum white signal;

    (b) black image signal parameter generating means responsive to transition of the video image signal from white to black to provide a black image signal parameter equal to smaller of said video image signal and a preset maximum black signal;

    (c) first means for combining said white and black image signal parameters to provide an offset parameter for the pixel being processed;

    (d) second means for combining said offset parameter with the video image signal of at least one neighboring pixel to provide a threshold level for thresholding said pixel being processed; and

    (e) thresholding means for thresholding said pixel with said threshold level.

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