func BlendFunc(sfactor uint32, dfactor uint32) {
	syscall.Syscall(gpBlendFunc, 2, uintptr(sfactor), uintptr(dfactor), 0)
}
func BlendFunc(sfactor uint32, dfactor uint32) {
	syscall.Syscall(gpBlendFunc, 2, uintptr(sfactor), uintptr(dfactor), 0)
}
func BlendFunc ( sfactor uint32 , dfactor uint32 ) { syscall . Syscall ( gpBlendFunc , 2 , uintptr ( sfactor ) , uintptr ( dfactor ) , 0 ) }
// specify pixel arithmetic
specify pixel arithmetic