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Method and apparatus for compressing color or gray scale documents

DC
  • US 5,778,092 A
  • Filed: 12/20/1996
  • Issued: 07/07/1998
  • Est. Priority Date: 12/20/1996
  • Status: Expired due to Term
First Claim
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1. A method for compressing a pixel map representation of a document, said pixel map representation having a resolution of X spots per inch, said method comprising the steps of:

  • a) creating a foreground pixel map from said pixel map representation of a document, said foreground pixel map having a resolution less than X spots per inch and containing color information for foreground elements of said document;

    b) creating a background pixel map from said pixel map representation of a document, said background pixel map having a resolution less than X spots per inch and containing image information for image portions and color information for non-foreground portions of said document;

    c) creating a selector map from said pixel map representation of a document, said selector map for selecting between pixels in said foreground pixel map and said background pixel map when decompressing said compressed pixel map representation of said document;

    d) compressing and storing each of said foreground pixel map and said background pixel map using a compression technique suitable for compressing images; and

    e) compressing said selector map using a technique suitable for compressing bitmaps.

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