[FeatureRequest] ApplyMask transform

[haarburger]

Description
Add a transform that applies a binary mask to an image

Proposal
Given a mask key, apply the mask to the image to set all background voxels to a predefined value

*Are you able/willing to implement the feature yourself (with some guidance from us)?
yes

[justusschock]

This might be a non-differentiable transform. We should check that and maybe add a warning if that's the case

[mibaumgartner]

Could this be implemented as a multiplication?

filtered = input * mask     # filter foreground
filtered += (1 - mask) * background_val    # set background value

This should be differentiable.

[justusschock]

@haarburger any progress on this? otherwise I would implement this :)

[haarburger]

Nope, haven't done anything so far.