GRUB Splash Image Information

There are 3 important things to know about GRUB's splash image support.

[1] The image needs to be in xpm format.
[2] The image needs to be 640x480 in size.
[3] The image must have only 14 colors.

The xpm file can be left as is or gzipped; grub seems to load gzipped images a bit faster. The thinking on this is that grub can load a gzipped image and decompress it faster than it can load the full size image, due to hard drive access times.

You can still change the foreground and background colors of grub's menu if you're using a splash image, but the image itself won't be affected, only the menu overlay.

Here are a couple ways to get an image in the format you want it:

The quick way: (using convert from imagemagick)

convert -resize 640x480 -colors 14 whatever.xpm && gzip whatever.xpm

The slow way: (using the gimp)

Open the image you want to use in the gimp, click the "Image" menu, then "Mode", then "Indexed". Select "Generate Optimum Palette:" and enter 14 for the maximum number of colors. It's also recommended that you check the "No Color Dithering" option.
After the conversion, save the file as whatever.xpm. The gimp should automatically create the correct format when it saves the file.

After you've gotten the image into the correct format and gzipped it (or not, your choice), all you need to do is add it to your grub config file, menu.lst (sometimes grub.conf, symlinked to menu.lst or a normal file, depending on your distribution.) The line you need looks something like this:

splashimage (hd0,2)/grub/crux02.xpm.gz

This example is from my system, where the image is called crux02.xpm.gz and is stored in /boot/grub. /boot is the 3rd partition on my system, so (hd0,2) is needed to point grub to the right place. As you might guess, grub numbers partitions and drives with a 0-origin. So (hd0,2) means the first hard drive, third partition. GRUB can read many different filesystems, including reiserfs and xfs, fortunately, so nothing funky is needed to get it to see the image path.

Reboot to test the image and you're done.