MATLAB Answers

## To tilt image backwards

Asked by nadine

### nadine (view profile)

on 4 Feb 2013

Hello, I hope I can describe the problem clear enough: I am displaying a 2D image (medical imaging) that i would like to tilt backwards (Or make it look like it is tilting backwards, since it is a 2D image and i am staying in a 2D space) Currently i am using the projective Transformation. So far I am putting in diffrent values for the Tform parameters, but I am doing it manually, which means, I would need either to find out the right parameters, to make the image tilt in the right way, OR find a function that does the calculation for me. Does anyone understand, and could give me advice, on how to make this work correctly? Thank you for your time.

Jan Simon

### Jan Simon (view profile)

on 4 Feb 2013

What is the actual question? What are the "right" parameters? Which calculation to want to be performed?

nadine

### nadine (view profile)

on 4 Feb 2013

Okay sorry for that: let me give you an example to clearify, you hold a sheet of paper in your hand in front of your face, now you tilt it backwards. The perspective changes... what to do to simulate that change of angles. Im doing my best here to describe, is it more clear now? thank you

## 2 Answers

### Image Analyst (view profile)

Answer by Image Analyst

### Image Analyst (view profile)

on 4 Feb 2013

How am I supposed to know the right transform? All I can suggest is Steve's blog for more examples: http://blogs.mathworks.com/steve/2006/08/04/spatial-transformations-defining-and-applying-custom-transforms/

nadine

### nadine (view profile)

on 4 Feb 2013

Thank you for your comment, unfortunately that is not what i am looking for.

Image Analyst

### Image Analyst (view profile)

on 4 Feb 2013

The imtransform() example in the help on Projective Transformation is an image that is tilted back. Why is that not what you looking for? I think it's what you asked for.

Answer by Jurgen

### Jurgen (view profile)

on 4 Feb 2013

Instead of doing it manually, use a for loop, compare with 'correct' reference image (e.g. sum of squared differences) and select the best transform at the end.

Only in some cases can you extract the parameters directly. I think one such an example would be radon transform with rotated images. Don't think projective has such a method.

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