A software library that is free and open source has been designed to manage icns files on OS X.
The best part of libicns is that it can fully read and write any 128x128 and all smaller 32-bit icons, and offer read support for 8-bit, 4-bit, and 1-bit icons. With Jasper linked to it, it offers full support for 512x512 and 256x256 32-bit icons with masks as alpha channels.
Moreover, libicns includes icns2png, a tool for extracting the images contained within icns files and saving them as PNG images. Besides, this software library also includes png2icns, a tool for creating icns files from a set of PNG images.
One of the great advantages of using libicns is that it should work on just about any POSIX/GNU compatible platform, including Linux, OS X, and various BSD implementations. It is a reliable and professional software tool that assists users in improving their workflow when working with Mac OS icns resource formats.
Version 0.7.1: N/A