How can I Align two images by using specifc coordinates of an object automatically?

I have a reference image, and a scanned image(for example). The scanned image does not have the same position as the reference image, how can I align them by using the black box on the left side of the reference image? I have the coordinates of the black boxes on the reference image, while the scanned image is unknown. I want it to align automatically after scanning the image. Thank you

Answer 1

[Image Analyst]

You can use imregister().

[Brink Azoa]

Can i have a example on how am I going to do it?

[Brink Azoa]

I tried the example on imregister.

>>moving = imread('MCQscan.jpg');

>> fixed = imread('MCQref.jpg');

>> imshowpair(fixed, moving, 'Scaling', 'joint');

>>[optimizer, metric] = imregconfig('multimodal')

>>movingRegistered = imregister(moving, fixed, 'affine', optimizer, metric);

I'm getting an error:

Error using imregtform>parseInputs (line 252) The value of 'MovingImage' is invalid. All dimensions of the moving image should be greater than 4.

Error in imregtform (line 123) parsedInputs = parseInputs(varargin{:});

Error in imregister (line 118) tform = imregtform(varargin{:});

[Image Analyst]

You did rotate scan by -90 and amde sure both were grayscale first, right? And both are at the same magnification, right? If they're not the same magnification then there's no way aligning one over the other would produce a good match. Attach your full code.

The error seems to be saying that your image is less than 4 pixels wide or 4 pixels tall. Why would it say that. What does this say:

size(movingImage)  % Don't use a semicolon!

[Brink Azoa]

This is my new code.....

moving = rgb2gray(imread('MCQscan.jpg'));

fixed = rgb2gray(imread('MCQref.jpg'));

imshowpair(fixed, moving, 'Scaling', 'joint');

[optimizer, metric] = imregconfig('multimodal')

movingRegistered = imregister(moving, fixed, 'affine', optimizer, metric);

figure

imshowpair(fixed, movingRegistered,'Scaling','joint');

and the resulting figure is in the picture, am I wrong in this code? thanks for helping....

[Image Analyst]

It's not meant for huge translations. Why did you not rotate the one so at least it's in the correct orientation like I suggested??? Use moving = imrotate(moving, -90) or something like that.

[Brink Azoa]

Hi I have tried the imrotate, and it works. But it only works when there are not any boxes that are shaded. I've tried it with boxes shaded,and everything went wrong... the same code but without rotation now... here are the scanned shaded picture(MCQshaded), and the reference, I have also tried a scanned image (test2.jpg) as my reference to align with MCQshaded.

[Image Analyst]

Of course, imrotate() works regardless if any boxes are shaded or not. Not sure what you're referring to when you say that.

If the presence of user-drawn stuff on the form confuses the imregister, then locate the registration set of bars on the left and make everything else white. Then call imregtform() to figure out the transformation, and then apply it to the original picture.

[Brink Azoa]

Oh sorry, I mean the imrotate() works on my code at the first set of images which is MCQref and MCQscan. In my second trial of the code without the imrotate(because the 2 images are at same position, but tilted slightly), when I scan a sheet with shaded box,the output of the pictures is not aligned anymore, using my whole code...

Ok thank you very much, I'll try imregtform....