CURVE-FITTING APPROACH FOR TANGENT ANGLE AND CURVATURE MEASUREMENTS

The measures of tangent angle and curvature of a digital curve play an important role in image analysis such as comer detection, ID shape re presentation and shape signature in the Generalized Hough Transform. I nstead of using the discrete measurement approach, the least-squares m ethod is employed to fit known digital points to two cubic polynomial functions, one with y = f(x) that minimizes the sum of the vertical di stances and the other with x = g(y) that minimizes the sum of the hori zontal distances from the known points to the approximated curve. The tangent angle and curvature are therefore directly computable from the first- and second-order derivatives of the continuous functions. Hybr id procedures are also proposed to select the better curve from f and g for accurate evaluation of tangent angle and curvature. Experimented results on both analytic curves and real-world images are included.