[opensuse-buildservice] Slightly Off-Topic: How to create bootsplash logo.mng?

Hi, I know, it's off-topic, but I was unable to find any _clear_ instruction on how to create bootsplash logo.mng files. Some e.g. state, that a special version of convert must be used, or sililar... Does anybody have a pointer on how to exactly do that on openSUSE (11.1)? -- With best regards, Carsten Hoeger