how to count boxes with only this camera direction

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Which algorithm do I apply for this problem? Canny Edges, Segmentation? I tried it but low accuracy.

Just collect some ideas and think of the different szenarios like what indicates you that for a given Pixel (x,y) there will be a neigborhood, connecting between BoxA, BoxB or/and other Boxes. So, it has pretty much to do with edge detection. So after adding some blur and doing canny edge detection, you'll have a binary image. With the given information inside your binary picture, you'll be able to use segmentation or find contours and fill in the areas of founded contours. But as always - this is just an idea and there are many ways to reach the point where it's working satisfactorily.