A method for calculating the tangent on the basis of the Hough transform

A method for calculating the tangent direction for a digital curve on the basis of the Hough transform is proposed. The initial data for the Hough transform are taken from tables of angular intervals obtained from a catalog of digital curves. Such a catalog is constructed for a chosen size of the local window on the basis of a specially developed indexation of curves. When determining the intervals of tangent directions for the catalog of curves, several methods of parameterization are used: straight line, elliptic or sinusoidal arc, and superposition of harmonics. The curve selection criterion is the maximum curvature of the corresponding smooth parametric curves. This makes it possible to adapt the method to a class of initial curves. Comparison with earlier-developed methods has demonstrated a significant increase in accuracy, especially with an increase in the curvature.