antsMotionCorr: center of rotation is not written

[oesteban]

I see that, for some reason, the affine matrices are not written: https://github.com/stnava/ANTs/blob/master/Examples/antsMotionCorr.cxx#L1078

Is there a reason for not writing them?

The problem is that the center of rotation is lost. Even though it is set on the center of masses, computing it with a different software will give slightly different values (also there is the orientation convention issue). This is an example for an image I just used:

python: -3.5478249 , -14.09039795,   0.74709859
ANTs:   3.5478134155273438 14.090387344360352 0.7471063733100891

To make antsMotionCorr reproducible, the FixedParameters of the transform should be written out somewhere. A use case (actually my problem): you want to apply the motion correction but using LanczosWindowedSinc interpolation. This is currently (AFAIK) not possible, since there is no way to feed the transforms into antsApplyTransforms. Am I right on this?

If I submit a PR, will it be considered anytime soon?
Are there any preferences on whether adding a flag to output the itk matrices or just appending the fixed parameters as MoCo parameters in the csv file?

Thanks very much

[satra]

@ntustison - what do you think?

[ntustison]

@satra sounds good to me if @oesteban wants to submit a PR. I'd look at it but, unfortunately, antsMotionCorr is one piece of ANTs code that I don't think I've ever touched.