Image segmentation, where to start?

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Hi There,

Quite new to image processing and OpenCV, I have for a task to segment an image as attached. The initial quality of the image cannot be improved.

The goal is to be able to segment each cell on that picture independently. The cell amount, size and arrangement may change so there is no way of applying some kind of static mask.

So far I've tried a few approach, one being Canny + Edge detection but this yields poor results.

As can be seen, the cells themselves are not homogeneous, although, the background is quite homogeneous. Is there some ways to segment that picture, perhaps using the background to be able to define lines ?

Thanks and cheers.

EDIT:

So far I've been able to produce this, which I guess is a good step.

Process was Filter2D, Adaptive Threshold, morphology & HoughLineP (in red).

However, I'm stuck into defining triangles, my guess would be to make some algorithm to define lines angles and then finding crossing points, although it's relatively complex. Would be some OpenCV functionality make the task easier ?