Color-depth and RLE
If you really have to include bitmaps in your preset, here are a few guides:
- Winamp scales the picture for you, so you can leave it at the minimum size.
- Less colors = smaller size. Never use a 24-bit/32-bit bitmap (except for tiny ones, but then the difference between 200bytes and 400bytes is insignificant), but rather a 256 colour image or lower. The reason is that 256-colour images or lower use a pallette: each color used is given a number. The image contains a lookup table to match a number to a colour. Then instead of the actual colour values, only the numbers are used. Compare an 8-bit number to a 24-bit colour value, and you'll soon understand the difference. Use the lowest possible amount of colours, but if your image is small enough (< 40KB?), you don't need to bother.
- Compress it. Contrary to popular belief, .bmp's do have a built-in compression system. It's a simple Run-Length Encoding (RLE) system. It will work nicely on images with lots of uni-coloured areas (screenshots of windows for example), but will totally suck on images that vary a lot (renders, photographs, etc). RLE is inferior to basically any other compression system for images, but you have to use the tools you're given. RLE only works on 4-bit or 8-bit images and not all programs can export it (it's still a .bmp, but with a special mode). Consult your graphics program's manual or help to find out if it's supported.