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Character recognition method utilizing compass directions and torsion points as features

  • US 5,659,633 A
  • Filed: 04/25/1994
  • Issued: 08/19/1997
  • Est. Priority Date: 11/29/1991
  • Status: Expired due to Term
First Claim
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1. A method of recognizing a character comprising the operations:

  • (a) measuring the angle of the tangent to the character at each of a plurality of sample points on the character;

    (b) assigning those points having a tangent direction within a first, small predefined angle from the vertical axis with values of Up (u) or Down (D) compass directions, and those points having a tangent direction within the first, small predefined angle from the horizontal axis with values of Left (L) or Right (R) compass directions;

    (c) selecting as special points at least those sample pointsi) at the beginning and end of said character;

    ii) whose compass direction is different than that of the previously selected special point;

    iii) whose compass direction is the same as the previous special point only if;

    a) there is at least one sample point, among the sample points between the two sample points with the same compass direction, which has no compass direction, andb) at least one of said sample points with no compass direction is a "torsion" point defined as a point having a tangent direction which is a significant local extremum among those sample points with no compass direction between the two sample points having the same compass direction;

    iv) which are torsion points;

    (d) arranging said special points according to predefined rules;

    (e) and utilizing the resulting arrangement of special points for recognizing the character.

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