Keep in mind I'm using Mac's Preview, hardly a powerful graphics tool. Anyways, I am attempting to resize a few gif files (not factoring in graphics quality, I simply want them larger in size). Should be easy enough? Well I went to Preview's Change Size menu, altered the dimensions to roughly what I wanted them to be, and saved them. It seemed alright at first, but when I opened the game where the gifs were used, the frames all had black backgrounds, while the unaltered originals were transparent. Preview does seem wildly unoptimised for gifs, not even having a function to play them, so I think its safe to say that's the problem. So what is the simplest method of resizing a gif, without getting my problem, and which definitely works on Mac?
This is different from other "make gifs transparent" questions, because I'm not looking for a way to make them transparent - the gifs already are. This is about the resizing process.
Also, for posterity, I'll add that it is a Pokemon fan game, which uses the old png sprites by default. Replacing these pngs with gifs works just fine, except that every now and then some of those gifs are hilariously disproportionate, with no larger-resolution gifs available on the net.