Before the rush

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by evan-pak

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I usually take a picture of bill or receipt using my mobile phone and store it in a computer. Is there any desktop or Web-based software which can straighten the photo of a paper and flatten it? For example I want to create a rectangular image without any distortion from this image.

enter image description here

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I don't think this is really on-topic, but there are a number of phone apps which do just what you want. I use an app called Genius Scan on my iPhone. – mattdm Mar 26 '12 at 11:11
Right, even cam scanner does it for Android but I need a desktop app or web based solution – SoulMan Mar 27 '12 at 17:55
This should be moved to stackoverflow, if really an automatic solution is/was required. – Unapiedra Apr 13 '12 at 19:08
Recent versions of Hugin, which is primarily a panorama-stitching program, are pretty good at automatically identifying horizontal and vertical control points. That might be a starting point for a solution. – coneslayer Apr 13 '12 at 19:24

Yes. This kind of distortion is known as "keyhole" or "perspective" distortion. Many commercial image processing programs include capabilities to correct it. An illustrated workflow using the GIMP (a free download) is illustrated at

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The title suggests that an automatic approach is sought. This one requires manual intervention. – Unapiedra Apr 13 '12 at 19:06
Yes, @Una, the title may suggest that, but the question seems to leave it open. Before voting (or suggesting) to close you should at least request a verification from the OP on that point. In fact, why would automatic solutions be off topic here, anyway? – whuber Apr 13 '12 at 20:58
I haven't, and I suspect the OP isn't around anymore. I don't believe that this is off topic. The reason, why I would suggest moving it to SO, is that it will get answered there. – Unapiedra Apr 13 '12 at 21:03
I'm curious why you think this would get answered over on SO, and not get closed the moment it lands? This is not a programming, language, or platform question...its a software question at worst, and still a photography question at best. Cropping and distortion correction are most definitely within the realm of on-topic here, and I think whuber has offered a decent starting point in his answer. Combined with a little Scriot-Fu, and this could probably be automated quite easily. – jrista Apr 14 '12 at 1:49

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