I don't know what a .webp file is but I don't like it. They're like a filthy prank version of the image/gif you're looking for. They make you jump through all these hoops to find the original versions of the files that you can actually do anything with.
Edit: honestly I assumed it had something to do with Google protecting themselves from image piracy shit
I think we generally agree but I just want to clarify anyways. I'm not saying we should use PNG to store frames from videos.
What I am saying however, is that we should replace PNG with a modern lossless image format that is more flexible so users don't have to deal with these issues. All this colorspace stuff should be automatically handled and I shouldn't have to worry about it not being lossless. If I want to save a frame of video, I should be able to do it using an image format that everybody recognizes and accepts, it should not be a huge hassle and it should be fully lossless.