Preserve .png transparency?

[aaronyih1]

My input images are pngs with a transparent background. When running morpher.py with python facemorpher/morpher.py --src=taylor.png --dest=kim.png --out_frames=kimtaylortransp --background=average --plot, the output produces pngs with a white background rather than a transparent one.

Since the --background=transparent flag produces a transparent background around the end result, I thought it would be possible to export the --background=averaged resulting png with a transparent background as well like the input image:

After playing around with the source code, I've found it more difficult than I thought it would be. Can anyone smarter than me think of a way to preserve .png transparency from input to output with the average effect on both the face but also the background?