Take the 2-minute tour ×
Super User is a question and answer site for computer enthusiasts and power users. It's 100% free, no registration required.

I use my iPhone to capture a painting. However, the angle was not perfect, so instead of getting a straight rectangle, I get a trapezium. However, I want to transform this trapezium back into a rectangle (using some affine transformation). However, I cannot find a good way to do it. Please advice.

share|improve this question
    
My guest would be I can select four points in the captured photo and define the other 4 points of the rectangle and have the software transform it for me based on the coordinates of these points. However, I cannot figure out how to do that with GIMP –  Phuong Nguyen Mar 9 '10 at 3:00
    
As in the dupe - have a look at Imagemagick imagemagick.org/script/index.php –  Linker3000 Aug 17 '11 at 9:43
add comment

4 Answers

up vote 4 down vote accepted

In GIMP, it is called the perspective tool. I think it is the same in Photoshop.

There is an icon for it in the menu on the left. It looks like a trapezoid with two arrows at the bottom corners.

share|improve this answer
    
Thanks. This is exactly what I am looking for. –  Phuong Nguyen Mar 9 '10 at 9:21
add comment

I know there already is an accepted answer, but Hugin that can also be used to fix perspectives in pictures, and is much better at it than a regular photo editing software. There is a tutorial on their website explaining how to do this.

share|improve this answer
    
Thanks. This software is amazing. It deserves to be an answer, though. –  Phuong Nguyen Mar 9 '10 at 14:26
add comment

ImageMagick gives you the -distort Perspective option. Like explained in Perspective Distortion:

convert image.jpg -distort Perspective '7,4 4,3 4,1 4,1 85,1 100,1 85,2 100,3' result.jpg

share|improve this answer
add comment

paint.net will do this - you're looking for the 'layers', 'rotate/zoom' option. just move the ball to get it aligned

share|improve this answer
add comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.