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ALIGNING A DATA TABLE WITH A REFERENCE TABLE

  • US 20170147552A1
  • Filed: 11/17/2016
  • Published: 05/25/2017
  • Est. Priority Date: 11/19/2015
  • Status: Active Grant
First Claim
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1. A method for aligning grid lines of an image of a table of a filled-out paper form with grid lines of an image of a table of a template of the filled-out paper form, the method comprising:

  • generating, by a computer system, a thin feature image of a filled-out paper form by;

    applying a median filter to an image of a filled-out paper form to generate a filtered image, wherein the applying of the median filter includes;

    for each pixel of the image of the filled-out paper form;

    selecting a plurality of pixels that have a pre-defined location relative to said each pixel,identifying a median pixel of a set of pixels comprised of the plurality of pixels and said each pixel, andgenerating the filtered image by replacing said each pixel with the median pixel, andsubtracting the filtered image of the filled-out paper form from the image of the filled-out paper form to generate the thin feature image,wherein the thin feature image includes grid lines of a table of the filled-out paper form;

    straightening, by the computer system, the grid lines of the table by;

    aligning the grid lines of the table with an X axis or a Y axis, the X axis being a horizontal axis and the Y axis being a vertical axis, by;

    for each sub-block of a plurality of sub-blocks of the thin feature image;

    calculating a plurality of Hough transforms for said each sub-block, each of the plurality of Hough transforms being calculated based on a different rotation of said each sub-block relative to the X axis or the Y axis,determining a dominant rotation relative to the X axis or the Y axis for said each sub-block based on the plurality of Hough transforms,calculating a transformation for said each sub-block based on the dominant rotation, wherein the transformation aligns lines in said each sub-block with the X axis or the Y axis, andapplying the transformation to generate a rotation aligned version of said each sub-block, andgenerating the rotation aligned version of the thin feature image based on the rotation aligned versions of the plurality of sub-blocks; and

    scaling and shifting, by the computer system, the rotation aligned version of the thin feature image by;

    determining a scale translation and a shift translation that maximizes a correlation between the grid lines of the table of the rotation aligned version of the thin feature image, and template grid lines of an image of a template table of a form template, andapplying the scale translation and the shift translation to the rotation aligned version of the thin feature image to generate a location aligned version of the thin feature image,wherein an alignment of the grid lines of the table of the location aligned version of the thin feature image with the template grid lines of the image of the template table facilitates a determination that the table and the template table are aligned.

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