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254 Bu il d Y o ur O w n Q u a d c o p t e r

Figure 9.33 Steam-engine valves, the original image. (Source: Wikipedia)

Figure 9.34 shows the post-processed image for the steam-engine valves. I did notice
that edge detection was not particularly successful in the portions of the image that had poor
contrast. For instance, look at Figure 9.35 where I circled the vertical pipe coming out of
the engine.
If you look at the same area in Figure 9.34, you can easily see the edges where the pipe
exits the engine cover and turns downward. The curved edges are readily detected by the
Canny edge detector. However, as the pipe descends, the contrast in the original image
becomes much poorer, and the edges disappear, as is evident in Figure 9.34. It is just
something to be aware of when post processing images. It is important to get as much light
on the subject as possible and to maximize all edge contrasts for best results.

Figure 9.34 Canny edge detection on the steam-engine valves. (Source: Wikipedia)