Can imregister provide transformation details on the registeration of the moving image?

I want to register and fuse two images, but I need to do some image processing of the images that I register, then use the translation and rotation details of the registration to fuse the unprocessed images. imregister only provides a transformed image, but no details on how it transformed it. Is there any way to get the details of the transformation to apply to my unprocessed images?

[Anita]

Richard, Can you please provide the modified imregister2 function which outputs tform?

[Sean de Wolski]

@Anita, I believe you just have to add tform as an output:

[moving_ref, tform] = imregister2(varargin)

Then copy the rest of its contents.

Answer 1

[Sonoma Rich]

I modified imregister to return the "tform" object that it uses for the transformation. I then created a copy of "transformMovingImage", a function within imregister so I can call it.

[optimizer, metric]  = imregconfig('multimodal');
[movingRegisteredProcessed, tform] = imregister2(movingProcessed,fixedProcessed,'rigid',optimizer,metric);
movingRegisteredUnprocessed = MyTransformMovingImage(movingUnprocessed, fixedUnprocessed, tform);
fused_image = imfuse(fixedUnprocessed,movingRegisteredUnprocessed,'blend');

This worked. It would be nice if the standard function provided the "tform" object.

Answer 2

[Alex Taylor]

As of R2013a, users who want access to the geometric transformation estimate computed by imregister can call the function imregtform. The function imregtform returns a geometric transformation object that can be applied to the moving image using the new function imwarp.

http://www.mathworks.com/help/images/ref/imregtform.html

The function imregister calls imregtform to obtain the geometric transformation that registers the moving image to the fixed image and then calls imwarp to produce the returned output image.

[Anthony]

Are you sure about that? The transformation I get using imregister() is not the same as using your method. Perhaps I have to specify those R things?

[Sean de Wolski]

In R2013b, imregister just calls imregtform on the first line. So it will depend on what you pass in...

[Alex Taylor]

Yes, I'm quite sure. When you call imwarp with the output tform, you will need to specify an 'outputview' so that imwarp knows the location and resolution you want for the resampled image. In most registration problems in the default coordinate system, you will define the output spatial referencing option (assuming 2d) as:

MovingReg = imwarp(moving, tform, 'OutputView', imref2d(size( fixed)));

This is shown in the examples in the help and documentation for imregtform.

Answer 3

[Ashish Uthama]

One possible approach:

If you add this parameter and value:

   'DisplayOptimization',true

to your call, you'll notice that imregister displays the affine transform it uses with imtransform to perform the final registration.

[Sonoma Rich]

I tried this, but I need the results as an object that I can work with it. This method just displays the transformation details, but I need to copy and paste it to use it.