annotations out of canvas are projected to edges incorrectly

[MuhsinFatih]

While I was playing with exported annotations, I noticed that they are not exported correctly when there is a segment with a point outside the boundaries of the canvas.
In coco_utils.py, the following lines do this:

x = _fit(round(center[0] + point[0], 2), image_width, 0)
y = _fit(round(center[1] + point[1], 2), image_height, 0)

Which simply takes points outside canvas to the edges. However that breaks the geometry:

I don't know if making sure all the segments are in the canvas is needed, so I tested it with _fit removed, and exporting & importing kept annotations as-is. I also used pycocoutils and imantics to do use annotations for computer visionry stuff and everything worked as expected, such as coco.annToMask(), which I had initially suspected might fail with points out of canvas.

I tried to implement a version where the points are projected correctly, but quickly realized that there is lots of edge cases, i.e. if you do segmentations around 3 quadrants it will do a shortcut between two edges and miss some of the area. I couldn't think of a solution that doesn't involve a bazillion if statements yet so I left my attempt there in paperjs_to_coco_cliptobounds() function, in case someone wants to take over where I left it