I was downloading some icon packs from the ever wonderful Smashing Magazine and some of them contained only files with a .icns extension, Apple’s icon image format. Ubuntu was having trouble opening them (I am guessing there are license issues of some sort preventing Canonical from shipping Ubuntu with the codecs for it installed by default), but as usual there is a fix right around the corner.
Simply install the package
icnsutils using your favourite method. E.g., in the
sudo apt-get install icnsutils
Now what this program provides is (amongst others) a utility to unpack the .icns file into a bunch of .png files. Simply navigate to your folder using a terminal and issue
Obviously replacing yourfile.icns with the file to unpack. Now you can get back to downloading yummy icon sets!
A commenter notes you can extract all sizes from all the icons in a directory at once by issuing
icns2png -x *