Image registration with different x and y scales

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Daniel Dickinson 2020-2-4

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/503686-image-registration-with-different-x-and-y-scales

评论： Daniel Dickinson 2020-2-5

I am attempting to use imregcorr to register 2d images obtained from a fluorescence microscope. I did

tform = imregcorr(MOVING,movingRefObj,FIXED,fixedRefObj,'transformtype','similarity','Window',true);
imwarp(MOVING, movingRefObj, tform, 'OutputView', fixedRefObj, 'SmoothEdges', true);

In these images, nearly all of the signal should be colocalized, but I see poor registration along the x-axis: the red signals at the left side are shifted left while the red signals at the right side are shifted right. Registration on the y-axis looks ok. The red channel is the moving image in this example.

imregcorr returns the following affine transformation matrix:

>> tform.T
ans =
    0.9863         0         0
         0    0.9863         0
    3.7267    7.7000    1.0000
    

The X and Y scale factors are both the same (0.9863), which seems suspicious to me; visually, it looks like the scale should be smaller along the x axis so that the image is stretched. I suspect that this function is somehow constraining the X and Y scales to be the same. Is there an option that allows them to be independent, or another function that allows registration with independent scaling of the two axes?

I have also tried imregister with both the "similarity" and "affine" options, but with similar results.

Thanks for any input.

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Alex Mcaulley 2020-2-5

Yes, they are really similar.. Can you share the original images (moving and fixed)? I can see in the composite what you say " the red signals at the left side are shifted left while the red signals at the right side are shifted right". If this happens in the original images, cannot be corrected with an affine registration.

Daniel Dickinson 2020-2-5

在 MATLAB Online 中打开

OriginalImages.zip

Sure, I'll attach two of the original images. Green is fixed and FarRed is moving.

If I understand correctly, the parts of the affine transformation matrix that govern scaling are

Xscale    0        0
0         Yscale   0
0         0        1

so shouldn't it be possible to introduce a non-uniform stretch (to correct the effect I'm seeing) if Xscale and Yscale are different? Xscale should be smaller than Yscale in this case. I'm just not sure how to do that with imregcorr (or if it's even possible).

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