Does the similarity transform implementation support reflection?

[tischi]

From Wikipedia: https://en.wikipedia.org/wiki/Similarity_(geometry)

In Euclidean geometry, two objects are similar if they have the same shape, or if one has the same shape as the mirror image of the other. More precisely, one can be obtained from the other by uniformly scaling (enlarging or reducing), possibly with additional translation, rotation and reflection.

In my hands it seemed as if reflection is not part of the current implementation, is it?

[bogovicj]

You're right that reflection is not included.

Bigwarp estimates the similarity (and linear transforms) using
https://github.com/axtimwalde/mpicbg/blob/cbbe21d78fef3c40a5da50f3bdb8da68b5c14b51/mpicbg/src/main/java/mpicbg/models/SimilarityModel3D.java

[tischi]

All right, I guess changing this to include reflection is out of scope?

Would it be possible to add a new class SimilarityWithReflectionModel3D?

I think we will be quite often having the use-case where we would need reflection but not full affine.

As a workaround, I have implemented in MoBIE a manual transformation just for reflections; so we are not totally stuck.

[bogovicj]

Adding something like that would be nice. Maybe the time is now to move those things from the mpicbg repo to imglib2-realtransform (?)

Will discuss with @axtimwalde