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System and method for dithering and quantizing image data to optimize visual quality of a color recovered image

  • US 5,905,504 A
  • Filed: 12/19/1996
  • Issued: 05/18/1999
  • Est. Priority Date: 04/15/1994
  • Status: Expired due to Term
First Claim
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1. A system for dithering and quantizing image data, comprising:

  • a plurality of dither tables corresponding respectively with a plurality of colors, each said dither table having dither noise values corresponding with a respective color; and

    a plurality of dithering and quantizationmechanisms associated respectively with each of said dither tables, each said dithering and quantization mechanism configured to generate a quantized dithered color value using a dither noise value retrieved from a corresponding one of said dither tables,wherein said system further comprises for each of said colors;

    a dithering mechanism for providing said dither noise value;

    a comparator for comparing a color value corresponding with the image data with a predetermined cutoff value;

    an aliasing mechanism for aliasing said color value with other color values below said predetermined cutoff value when said color value is less than said predetermined cutoff value to derive an aliased color value;

    an offset mechanism for modifying said dither noise value when the color value is greater than said predetermined cutoff value to derive a modified dither noise value;

    an adder for generating said dithered color value, for mathematically combining said dither noise value with said aliased color value, and for mathematically combining said modified dither noise value with said color value;

    a clamp for insuring that said dithered color value resides within a predetermined color range; and

    a quantizing mechanism for quantizing said dithered color value to derive said quantized dithered color value for storage in memory.

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