[color:"orange"]bitmaps(I'm not sure if it is the same in English)[/color]
It is.
Many image viewers with basic editing features (such as
IrfanView or
XnView) can do batch conversions, and there are specialized programs as well (see NConvert on the XnView site, for example).
I have not used Fraps, but it is popular enough there should be a few tutorials or guides online about minimizing file size. Lowering the game resolution would be the easiest way to drop the video file size, and you can also lower the fps to capture in Fraps (though too low and the video will not be as smooth).
Fraps saves as (mostly) uncompressed video in order to minimize the impact it has on the game (see its
FAQ), but you can use a video editor (such as
VirtualDub or
ZS4) to trim unnecessary bits and convert to a more efficient format.