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The task is: Find all 4 corners of a given red polygon on this image

I know how to find all corners if all borders are visible (linear extrapolation, phew, easy).

My question is how to go about finding bottom corners if we don't see the bottom border?

eshirima
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captain.murphy
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  • you can't. How should that be possible? If there is a single corner missing, you could compute intersection (if the lines are straight or following some extrapolateable curve), but that doesn't work if there are no intersecting lines present, because one line is completely missing. In your sample image, you the angle and position of the "bottom-left" line which you should intersect with the "left" and the "right" line. – Micka Aug 17 '17 at 13:33
  • I see a red quadrilateral in the image. – dhanushka Aug 18 '17 at 06:34

1 Answers1

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The answer is quite simple. You can't.

If you don't have both dimensions of your rectangle you cannot find missing corners. You cannot know how far that rectangle extends outside your image.

For your example the only way would be to assume that corner 3 is on the image border. Then you can calculate the missing 4th corner.

Piglet
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