E1C07 09/14/2010
14:43:52 Page 301
the coins is to subject the image to a process called thresholding. In this process all pixel values
above a certain level are set to pure white, and all below are set to pure black. Let’s threshold our
image at a level of 127. The resulting image is shown in Figure 7.33. When we apply the same edge
detection methods used on the grayscale image, the image shown in Figure 7.34 results. Clearly this
is a step closer to finding the edges of the coins.
(a)
(b)
Figure 7.32 Edge detection methods. (a) Sobel method of edge detection.
(b) Canny method of edge detection.
7.10 Digital Image Acquisition and Processing 301
14:43:52 Page 301
the coins is to subject the image to a process called thresholding. In this process all pixel values
above a certain level are set to pure white, and all below are set to pure black. Let’s threshold our
image at a level of 127. The resulting image is shown in Figure 7.33. When we apply the same edge
detection methods used on the grayscale image, the image shown in Figure 7.34 results. Clearly this
is a step closer to finding the edges of the coins.
(a)
(b)
Figure 7.32 Edge detection methods. (a) Sobel method of edge detection.
(b) Canny method of edge detection.
7.10 Digital Image Acquisition and Processing 301