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Error diffusion method and apparatus

  • US 6,678,073 B1
  • Filed: 02/08/2000
  • Issued: 01/13/2004
  • Est. Priority Date: 02/08/2000
  • Status: Expired due to Term
First Claim
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1. A method of diffusing error caused by quantizing each pixel within an image formed of a plurality of pixels, each pixel representing a greyscale value of the image at a location (n, l) within the image, and having an original greyscale value associated therewith, the method comprising:

  • (a) adding to the original greyscale value of a pixel having a position (n, l) within the image a first error term resulting from quantization of previously processed pixels to derive a modified greyscale value;

    (b) comparing the modified greyscale value of the pixel with a threshold to select an output value representing the pixel;

    (c) calculating a second error term having a value that is the difference between the output value and the modified greyscale value;

    (d) distributing the second error term to a preselected plurality of neighboring pixels at positions (n+1, l), (n−

    1, l+1), (n, l+1), (n+1, l+1) using a linear phase filter algorithm having a set of distribution coefficients with a sum less than one, wherein one of the coefficients within the set of coefficients is combined with the second error term for each pixel position; and

    (e) repeating steps (a)-(d) for each pixel within the image.

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