Edge Direction Confidence Estimation for Improvement of Hough Accumulation

The Hough transform silhouette identification method requires a consistency of edge direction in the identification of similar silhouettes. Many gradient operators used in Hough preprocessing require a thresholding and a non-maxima suppression routine to aid the localization process. These routines may delete edges or cause edge fragmentation. These anomalies degrade the Hough performance due to the lack of accurate silhouette extraction, and reduce the correct localization in the Hough accumulator. Noise or sampling errors can be removed by several enhancement routines presented. They are mean, median, symmetric nearest neighbor, hi pass, and low pass filters. An edge detection process is presented which produces a directional image and the confidence image that allows subsequent image analysis the ability to determine if the detected original edge orientation is accurate, and to what degree. The orientation confidence is produced by comparing a 7 by 7 operator and the Compass Gradient operator. This allows the Hough process the ability to modify the position of accumulation, thereby improving the Hough localization process.