A pseudo top-hat mathematical morphological approach to edge detection in dark regions

Edge detection is an important pre-processing step in image segmentation. Conventionally, edges are detected according to gradient property, then processed by the thresholding technique. By such an approach, fine edge details in dark region of the image are eliminated. It is annoying sometimes as they are as useful as those in bright region, although this is caused by unevenly distributed lighting in many machine vision applications. In this paper. a novel mathematical morphological edge detection algorithm. based on pseudo top-hat transformation which is derived from top-hat transformation, is proposed to preserve these edge details as well as prominent ones. The algorithm is also presented in detail. Comprehensive experimental results show that the proposed algorithm is efficient for edge details extraction in place of shading while preserving distinguish features. (C) 2001 Pattern Recognition Society. Published by Elsevier Science Ltd. All rights reserved.