How do I get the width and height ratio of a sheet of paper (or some other rectangular thing) from an image? Here is an example/image that maybe makes my question a bit clearer, https://i.stack.imgur.com/3TcJn.jpg . I know the coordinates of the corners of the paper in the image. I guess it is impossible to get the true width and height of the paper, but it should be possible to get the width and height ratio of the paper, right?
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Assuming all 4 corners of the paper are 90 degree angles, then yes, you should be able to get a ratio. Is there a formula you have tried so far? – Neil N Feb 23 '15 at 20:00
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@NeilN No, I am looking for a formula, but cant seem to find one. I have tried to derive one by myself, but with no luck. Was hoping someone here would be able to do it or give me any suggestions.... – lijas Feb 24 '15 at 18:25