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Compression/decompression algorithm for image documents having text, graphical and color content

  • US 6,587,583 B1
  • Filed: 09/17/1999
  • Issued: 07/01/2003
  • Est. Priority Date: 09/17/1999
  • Status: Expired due to Fees
First Claim
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1. A computer program product for compressing data files representative of an image document having color information and/or graphical information, said software product disposed on a computer readable medium comprising instructions for causing a computer to:

  • provide a first image file resolution of said document at a first and a second image file at a second resolution of said document with said-second resolution being lower than said first resolution;

    process the first image file to convert the first image file into a text file representation of the document;

    compress said text file representation of the document to provide a first compressed file;

    process said second file to extract information from the image representation of the document corresponding to color information and graphics information;

    compress the second file using a second compression technique to provide a second compressed file containing information corresponding to the image;

    store said first and second compressed files and color information to provide a composite compressed file corresponding to the document;

    scan the document at a first resolution to provide said first image file at said first resolution and scan the document at a second resolution to provide said second image file at said second resolution;

    determine the foreground color corresponding to colors associated with text positions of the document; and

    determine the foreground colors by causing the computer to retrieve a plurality of samples of blocks of pixels from the low resolution image representation of the document and from each one of said samples of pixels find a pixel corresponding to the minimum and maximum intensity of -the pixels in the block;

    and for each one of said samples calculate a threshold value representative of the document by averaging the minimum and maximum intensities for each of the blocks;

    determine a color associated with each one of the blocks and the width of intensity of each one of the blocks and provide a data structure having an entry for each one of said blocks corresponding to a foreground color.

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