fivecat posted at 6:48PM Tue, 19 April 2016 - #4266221

For a free video editor, you could try virtualdub.

While it is technically an editor, I tend to think of virtualdub as more of a video processor. It lacks a lot of basic editing functions, but does have loads of useful filters and functions for improving individual clips. It's just that when you start working with more than one clip you quickly see how limited its editing functions really are.

Virtualdub would be my recommendation for the first part of the OP's question. If the images are numbered sequentially, simply loading the first one will cause virtualdub to load the successive frames (they must all be the same size/aspect as the first image) and create an animation/video.

The first problem though is that virtualdub doesn't preserve the alpha channel when it imports the frames. It doesn't support true 32 bit color, as its 32 bit color depth only adds a dummy alpha channel. I'm honestly not sure which video formats do support transparency. Maybe animated .gifs can have masks? It may not even be a limitation of the video format, possibly virtualdub just doesn't support an alpha channel.

If you were wanting to composite the animation in a more full-featured program such as Vegas, you could use a bright green or blue instead of the transparency and set up chroma key in the video editor for that layer. I'm not very familiar with Powerpoint, but I doubt it has a chroma key for video.