Questions and postings pertaining to the usage of ImageMagick regardless of the interface. This includes the command-line utilities, as well as the C and C++ APIs. Usage questions are like "How do I use ImageMagick to create drop shadows?".
GRUB does not just take any XPM image, but a very very specific form of XPM image.
I am not certain of the exact needs, but I think it was a limited set of colors and only single character color indexes. I suggest you check the GRUB documentation, forums, and other website for the exact requirements needed.