Alpha compositing

[KenSeehart]

It would be really nice if winmorph could handle the alpha channel
correctly. If it did, that would make it possible to animate a morph
over a background. Specifically, if I have a pair of png with partial
transparency, I would like to morph one into the other such that the
resulting sequence of images contain partial transparency. The
resulting sequence could then be used in an animation over a fixed
background image. IMO any morphing software without this feature is
basically useless for serious applications. All it involves is
morphing all four channels (RGBA) instead of just RGB, so it's pretty
trivial to implement.

My usage case would be:
1. Use Photoshop to extract the desired foreground objects from the
stock images to produce a pair of semi-transparent RGBA png files.
2. Use Morpheus to morph between these two RGBA png files to produce a
sequence of RGBA png files.
3. Use my own software to animate the result by displaying the RGBA
image sequence on top of a background.

The absence of this feature means that the backgrounds of the of the
original images are included in the morph, which means the result is
not even close to photo-realistic regardless of the quality of the
morph operation. Alpha composition would solve this problem.

Other users (not myself though, since I do the last step myself) may
benefit from a companion feature where the user supplies a background
image as well as the two foreground images to be morphed. The result
would be a morph against an undisturbed background.

If you don't know what "Alpha compositing" means, please don't bother
to attempt to answer this. Thanks.

Ken