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  • US 8,472,726 B2
  • Filed: 01/07/2011
  • Issued: 06/25/2013
  • Est. Priority Date: 01/07/2011
  • Status: Expired due to Fees
First Claim
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1. A computerized method comprising:

  • a. obtaining a first digital image of a first document page;

    b. obtaining a second digital image of a second document page;

    c. performing global geometrical transformation on at least one of said first and second digital images to obtain first and second aligned digital images;

    d. selecting a window of said first aligned digital image;

    e. selecting a window of said second aligned digital image;

    f. estimating residual local geometrical shifts, radiometric differences and blurring differences between said selected windows to obtain a second transformation;

    g. applying said second transformation to at least one of said windows;

    h. repeating steps (d) through (g) for consecutive windows of said first and second aligned images to obtain first and second similar images;

    i. comparing said first and second similar images to obtain a difference image;

    j. analyzing said difference image to determine whether at least one of the group consisting of;

    characters, images and components thereof have been added, deleted, changed or shifted; and

    k. displaying said differences.

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