Replace alpha in image with white colour | Mac

Bunch of images with alpha colour. Task is to post those images (one at a time, every few days) to Facebook, Twitter.  Problem is - once uploaded - alpha is removed and it shows black background instead.

Ugly!

So, I found this cool little app, that removes Alpha channel from images. (Drag and drop) But it then again is black. I tweaked code a little bit and uploaded it to GitHub - maybe it will be handy to someone also. It sure was helpful for me... (100 images in few seconds, and I can move on with my life on some more interesting tasks :) )

https://github.com/GuntisTreulands/Alpha-Channel-Remover