Transparent interpolate?

[ulatekh]

I have images with transparent backgrounds on which I'm trying to do motion interpolation. I looked at the code, and thought I made all the necessary changes, but apparently I'm missing something.

My work can be found at https://github.com/ulatekh/slowmoVideo/tree/transparent_interpolate . (The change to src/lib/ffmpeg_writer.cpp is just a hack; once the feature is working, I'll make all the little changes necessary to allow the user to set the pixel format.)

Transparency is partially getting through the system; if a frame doesn't need to be interpolated, it ends up in the output file properly transparent. It's just that any frame subject to interpolation gets its transparency wiped out.

Do you know what I'm missing here?

[ulatekh]

So far, I've determined that OpenCV optical flow apparently doesn't support transparent pixels, e.g. Farneback takes greyscale images as input. Also, I'm having pretty good results using the Deformations->Morph[interactive] filter in GIMP's G'MIC plugin.