From Just Solve the File Format Problem
DeskPic is a graphics program for the Atari line of computers.
.gfb files begin with ASCII "
The GFB image format: ------------------- It is a format that I use for the program GemFrac had once developed. The following data can be found in this image format: 4 bytes identifier (GF25 in this version) 4 bytes number of colors. 4 bytes width of the screen 4 bytes height of the screen 4 bytes size of the buffer to be allocated for the screen n bytes of graphic data, where n = ((image width + 7) / 8) * image height * planes, which corresponds to the largest allocated buffer. 768 bytes color table => max. 256 colors.