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Strokes localization by m-array decoding and fast image matching

  • US 7,570,813 B2
  • Filed: 08/27/2007
  • Issued: 08/04/2009
  • Est. Priority Date: 01/16/2004
  • Status: Expired due to Fees
First Claim
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1. A method for determining a path of a pen tip of a pen within a document, the method comprising:

  • (A) calibrating the pen in order to obtain a calibration parameter;

    (B) analyzing a watermarked document image in order to determine areas where x-y positions cannot be uniquely determined by m-array decoding;

    (C) segmenting a maze pattern from an obstruction component of a captured image, wherein the obstruction component comprises document content that occludes the maze pattern;

    (D) analyzing the maze pattern to extract bits from the maze pattern of the captured image;

    (E) in response to (D), determining a transform that transforms image position coordinates to actual position coordinates, wherein the actual position coordinates identify a location of the pen tip in relation to the document;

    (F) decoding the extracted bits associated with the captured image;

    (G) in response to (F), if the image position coordinates of the captured image cannot be determined, matching the captured image with image information, comprising;

    (i) warping the captured image to create a warped image; and

    (ii) matching the warped image with an area of the document, where a corresponding x-y position cannot be uniquely determined by m-array decoding;

    (H) determining image position coordinates of other image frames that are associated with a pen stroke, comprising;

    (i) matching a corresponding captured image with a neighboring area of the image position coordinates of an image whose image position coordinates have been determined previously; and

    (ii) repeating (i) until all image frames of the pen stroke are processed; and

    (I) mapping the path of the pen tip from the transform, the calibration parameter, and the image position coordinates.

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