What you said, is quite a project, not a question. I’d rather to study more about the similar projects and ask about some details in here. Although I could give you some hints:
1-Do a suitable thresholding on your image, like Otsu method (with a little change in the threshold value if it’s needed).
2-On the binary image do an erode and a dilate successively to get rid of the small objects.
3-Do a horizontal dilation to get all parts of a curve stuck together. This gives you two firm curves.
4-Find connected components of each curve and with their prositions, find the lowest pixels (local minimum of signals)
5-Horizontal position of these local minimums, gives you the frequency.
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solved Extract a periodic pattern from an image in Matlab