Most avatars seem to be resized imaages or animated gifs. In my case, I take the easy and quick approach of taking a screenshot from my LCARS system and just clipping out a rectangle of the required size with MS-Paint and saving it as a png file, since png is well suited for LCARS clips. In that unusual scenario, no resizing is necessary.
If it were a photo, I'd probably make it jpeg but not use MS-Paint, since there are many programs that convert a bmp file to jpeg of better quality. Still gif is okay, too, but gives you lower color depth.
Here's another example of clipping a detail rather than resizing:
If it were a photo, I'd probably make it jpeg but not use MS-Paint, since there are many programs that convert a bmp file to jpeg of better quality. Still gif is okay, too, but gives you lower color depth.
Here's another example of clipping a detail rather than resizing:
