Comparing patterns on coins.

asked 2016-03-04 13:57:29 -0600

Hello. I'm having a trouble comparing patterns on coins. I have fully working comparison of diameters, but some coins sadly have the same diameter. How can I accurately compare these patterns. I'd like it to be rotation invariant. It doesn't have to be scale invariant, because camera is always on the same height. I tried many things. I tried feature detectors like SIFT, SURF, FREAK, but i couldn't get anything to work properly. I don't want to use learning machine.

What would be the best method to use in comparing images like these? All help appreciated.

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answered 2016-03-04 19:18:46 -0600

Tetragramm

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There is a function that should do exactly what you need, and it works with the images you have provided here. The huMoments are invariant to scale, rotation, and reflection.

Just take your binary images and run them through cv::moments, cv::huMoments and compare the results (You can see the L1, L2 and L3 comparisons HERE).