How to perfectly align 2 scanned multiple choice paper images?

I there a way somehow to align 2 scanned multiple choice paper images? Maybe by using a bar code to auto align them or using a specific shape so i can compare or find the differences in the answers between the two papers?

Thanking you in advance.

Answer 1

[Image Analyst]

Yes. See the imregister() function in the Image Processing Toolbox.

[Vic]

I understand that this method creates a copy of the two images in one. But what I need is to correctly align the wrongly aligned image according to the correct other aligned image.

Align this image ( http://tinypic.com/view.php?pic=2ntjqiq&s=6 ) to the same position and alignment of the correctly aligned image( http://tinypic.com/view.php?pic=24pmgbb&s=6) so when I fuse them together I can almost see one correctly aligned image. Is it possible with the imregister??

Thank you!

[Image Analyst]

Yes. It doesn't create a copy of the two images in one. Did you look at the first demo:

fixed  = imread('pout.tif');
moving = imrotate(fixed, 5, 'bilinear', 'crop');

"moving" is the "repaired/aligned" image. Perhaps you were thinking of a display utility showpair()???

[Vic]

ok but I want to aligh this image http://tinypic.com/view.php?pic=2ntjqiq&s=6 to he same position and alignment of this image ( http://tinypic.com/view.php?pic=24pmgbb&s=6 ). I tried the code you have suggested by doing this : fixed = imread('aligned image'); moving = imread('wrongly aligned image');

... but i get some errors

Error using imregister>parseInputs (line 189) Argument 'MovingImage' failed validation with error: Expected input number 2, moving, to be two-dimensional.

Error in imregister (line 92) parsedInputs = parseInputs(varargin{:});

Error in Untitled12 (line 11) movingRegistered = imregister(moving,fixed,'rigid',optimizer,metric);

Any ideas?

[Walter Roberson]

Convert the images to grayscale before aligning them.

[Image Analyst]

The alignment will probably be the same on a monochrome image as if you could do it on a color image. Just apply the transform you get to all three color channels one at a time and recombine into a color image.