Abstract:

A universal sub-pixel edge detection algorithm is proposed based on extremal gradient, with the purpose of further improving the universal character and precision of traditional algorithms. Extremal gradient is disintegrated into positive and negative gradients that are solved respectively in eight directions. Then, initial edge composed of two types of pixels with local gray level maximum increase and decrease can be obtained. Finally, sub-pixel orientation fitting models are built for different types of edges separately according to the characteristic of initial edges. Experiments between the proposed algorithm and the others have been realized to verify its performance based on simulative and real images. The results indicate that the proposed algorithm has better applicability of different types of edges and higher precision including corner point than traditional algorithms. Therefore, this algorithm is effective in image edge detection.

Key words: edge detection, extremal gradient, sub-pixel edge, edge orientation