Abstract:

 Based on the improved Canny operator, the modified templates of size 3×3 were extended to the ones of size 5×5 via half-pixel interpolation method, and the method of maximum value of normalized autocorrelation was used to determine the edge direction so as to mitigate the broken edges or false edges due to the effects of noise. In the experiment, we used receiver operating characteristic curves to evaluate the performance of the algorithm. The results show that the modified Canny operator improves the effect of the detection, for it can accurate the edge direction while reducing the probability of false edge points, especially for that of the images rich in line edge.

Key words: Canny operator, edge detector, halfpixel interpolation, normalized autocorrelation, ROC curve