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Method for determining coordinates of circumscribed rectangular frame of each character for use in optical character reader

  • US 5,054,091 A
  • Filed: 04/18/1990
  • Issued: 10/01/1991
  • Est. Priority Date: 04/18/1989
  • Status: Expired due to Fees
First Claim
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1. A method for determining coordinates of a circumscribed rectangular frame for enclosing each character based on image data of character images in a recognition area having been read by an image scanner, including:

  • a first step of determining specified image data of a predetermined data unit in a transverse direction parallel to lines including at least one bit of black pixel by scanning said read image data, and for determining a specified bit being one bit of black pixel in said specified image data;

    a second step for judging whether a bit of black pixel is in either the bit located by one bit at the upper side of said specified bit of said specified image data which has been determined at said first step, or the bits located in said transverse direction by one bit of the bit located at the upper side by one bit of said specified bit of said specified image data;

    a third step for determining the bit of black pixel as a newly specified bit if there is the bit of black pixel therein and for repeating said second step, otherwise the coordinate in the transverse direction of said specified bit of black pixel being determined as a top coordinate of said circumscribed rectangular frame;

    a fourth step for judging whether a bit of black pixel is in either the bit located by one bit at the lower side of said specified bit of said specified image data which has been determined at said first step, or the bits located in said transverse direction by one bit of the bit located at the lower side by one bit of said specified bit of said specified image data;

    a fifth step for determining the bit of black pixel as a newly specified bit if there is the bit of black pixel therein and for repeating said fourth step, otherwise the coordinate in the transverse direction of said specified bit of black pixel being determined as a bottom coordinate of said circumscribed rectangular frame;

    a sixth step of calculating histogram data composed of either logical products or logical sums of respective bits in said transverse direction from plural image data located in a specified area between said determined top and bottom coordinates in a predetermined threshold range in said transverse direction from the center of said specified image data which is equal to or larger than the maximum of the transverse width of each circumscribed rectangular frame;

    a seventh step of determining a coordinate in said transverse direction of a bit of black pixel located at the leftmost position in said calculated histogram data as a leftmost coordinate of said circumscribed rectangular frame; and

    an eighth step of determining a coordinate in said transverse direction of a bit of black pixel located at the rightmost position in said calculated histogram data as a rightmost coordinate of said circumscribed rectangular frame.

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