I started writing my own chunky versus planar rountine but ofcourse somebody already did that.
I found this totally execellent package at Aminet: GetImage: http://aminet.net/package/dev/c/GetImage
This takes an image (or multiple image inside a Dpaint Brush) and converts it to a C Image data structure ready to by used.
I you're starting with a .png file you can use e.g. Personal Paint to convert it to an DPaint brush.

On the amiga we can include this file and avoid having to do any (slow) chunky/planar conversions, on other platforms we can just include the original .png file.
Excellent!