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Procedure to Accumulate Circles
• Set accumulator array A to all zero.
   Set point list array PTLIST to all NIL.
• For each pixel (R,C) in the image {
      For each possible value of D {
            - compute gradient magnitude GMAG
            - if GMAG > gradient_threshold {
                . Compute THETA(R,C,D)
                . R0 := R - D*cos(THETA)
                . C0 := C - D* sin(THETA)
                . increment A(R0,C0,D)
                . update PTLIST(R0,C0,D) }}