One suggestion would be switching to a grayscale camera. There is no reason for a color camera to be used in this application. It would improve the details in the image.
Will real cracks look like this? These look like a notch was cut in the rail with a radial saw.
Brighter lighting might improve the contrast between the rails and the cracks. It looks like the cracks will be black no matter what, so with high enough contrast you could pick them out fairly easily. Using a vertical edge detection matrix in the convolution vi would probably highlight the edges nicely. Something like:
1 1 1 1 1 1 1
1 1 1 1 1 1 1
1 1 1 1 1 1 1
0 0 0 0 0 0 0
-1 -1 -1 -1 -1 -1 -1
-1 -1 -1 -1 -1 -1 -1
-1 -1 -1 -1 -1 -1 -1
This would highlight the top edge of the crack without highlighting much else. Perhaps after that you could use a fixed threshold and see if any crack segments show up.
Bruce
Bruce Ammons
Ammons Engineering
