Does the G'MIC (Grey's Magic Image Converter) library work on iOS ?
what steps i should take in order to begin adapting it?
this is library link http://gmic.sourceforge.net/gimp.shtml
So long as it's written in C++, it should have no problem running on an iOS device. You could even write a thin ObjC++ wrapper for it to make your life a bit easier, but in it's current form, it should work smashingly.