Feature Extraction and Image Processing

130 Feature Extraction and Image Processing

The results for all edge operators have been generated using hysteresis thresholding

where the thresholds were selected manually for best performance. The basic first-order

operator, Figure 4.31(b), responds rather nicely to the noise and it is difficult to select a

threshold which reveals a major part of the pitus border. Some is present in the Prewitt and

Sobel operators’ results, Figure 4.31(c) and Figure 4.31(d), respectively, but there is still

much noise in the processed image, though there is less in the Sobel. The Laplacian

operator, Figure 4.31(e), gives very little information indeed, which is to ...