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Method for automatic recognition of two-dimensional shapes

  • US 4,573,197 A
  • Filed: 12/13/1983
  • Issued: 02/25/1986
  • Est. Priority Date: 12/13/1983
  • Status: Expired due to Term
First Claim
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1. A method of automatically recognizing objects comprising:

  • a. scanning said objects with a scanning means such as a video camera to produce signals representing each of said objects;

    b. converting the signals into a digital image where the pixel coordinates of the boundary of each object have been identified and stored as data;

    c. calculating from said data a series of Fourier coefficients c1 associated with the boundary of the object;

    d. testing a given number N of the Fourier coefficients, except for the zero order Fourier coefficient, in a predetermined order for absolute values which exceed a predetermined value and generating a series of integers sn with values corresponding to the subscript of each coefficient tested having an absolute value exceeding the predetermined value, so that;

    s1 =the subscript value of the first Fourier coefficient tested whose absolute value exceeds the predetermined value;

    s2 =the subscript value of the next Fourier coefficient tested whose absolute value exceeds the predetermined value;

    etce. calculating a first descriptor S as the number of Fourier coefficients cs.sbsb.n, whose absolute values exceed the predetermined value, identified in step b;

    f. calculating the greatest common divisor r of the integers;

    
    
    space="preserve" listing-type="equation">s.sub.n -s.sub.1, n=2, . . . , S Eq. 9g. calculating an integer J which is the smallest of all integers R which satisfy the condition that r is the greatest common divisor of the integers;

    sn -s1, n=2, . . . , R Eq. 10h. calculating second descriptors an as the absolute values of the Fourier coefficients c1 whose absolute value exceeds the predetermined value, according to the definition;

    
    
    space="preserve" listing-type="equation">a.sub.n Δ

    |c.sub.s.sbsb.n |, n=1, . . . , J Eq. 11i. calculating a series of third descriptors bn,j according to the following definition;

    
    
    space="preserve" listing-type="equation">b.sub.n,jΔ

    c.sub.s.sbsb.1.sup.(s.sbsp.n.sup.s.sbsp.j.sup.)/r c.sub.s.sbsb.j.sup.(s.sbsp.1.sup.-s.sbsp.n.sup.)/r c.sub.s.sbsb.n.sup.(s.sbsp.j.sup.-s.sbsp.1.sup.)/r, n=J+1, . . . , S;

    j=2, . . . , Jj. storing at least the first, second and third descriptors in a digital memory; and

    k. comparing the stored descriptors with descriptors of other objects calculated according to steps c-i to thereby automatically recognize objects of the same shape.

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