extract rectangular image from scanned image

I have scanned copies of currency notes from which I need to extract only the rectangular notes. Although the scanned copies have a very blank background, the note itself can be rotated or aligned correctly. I'm using matlab. how do I extract the currency part and get it aligned to the horizontal axis. I have tried using thresholding and canny/sobel edge detection to no avail. I used the below code but it works only for aligned images and not for rotated images.

<< input image

output image

>>

[hamida]

Affy, please can you tell me how you solved this problem.

Answer 1

[Image Analyst]

Did you see my answer to your prior question: http://www.mathworks.com/matlabcentral/answers/182427#comment_271921

Did you look up "registration" in the help and try any of the examples with your image?

[AFFY]

Yup but i couldn't extract the image with the help of your code. I tried thresholding, filtering and finding 4 corners in the image to get it rotated but it din't work either.

Answer 2

[Image Analyst]

I'll be traveling today and not have much time. I'm attaching another demo that uses the radon transform to do rotation. Give that a try.

[AFFY]

provide me with the codes of the above demo

[Image Analyst]

It's under the image.

[AFFY]

that isn't helping either.

[Image Analyst]

Then try another method. I'm getting ready to fly to Arizona today and will not have much time to help anyone.