for i in range (0, edges.height):
    for j in range (0, edges.width):
#        perpendicular = math.atan2(dx[i][j], dy[i][j])
        perpendicular = float (math.atan2(cv.Get2D(dx, i, j)[0], cv.Get2D(dy, i, j)[0]))
        slope = math.tan(math.pi/2.0 + perpendicular)
        for cy in range (0, edges.height):
            cx = int ((i-cy)*-1*slope / math.pow(a, 2) + j)
            ry = int (math.sqrt(a*a*math.pow(j-cx, 2) + math.pow(i-cy, 2)))
            if cx >= 0 and cx < edges.width and cy >= 0 and cy < edges.height and ry <= edges.height/2 :
                votes[cx][cy][ry] += 1
                if votes[cx][cy][ry] > maxVote:
                    maxVote = votes[cx][cy][ry]
                    maxCx = cx
                    maxCy = cy
                    maxRy = ry