I’m wondering if Intaglio can be used to make application icons for apps, both Mac OS and iOS? It looks perfect for the job but I’m not sure if the export capability exists?
There are details here of how to turn an iconset (essentially a directory containing a bunch of icons at different sizes) into an icns using the iconutil command line tool.
Use iconutil to Create an icns File Manually
The iconutil command-line tool converts iconset folders to deployment-ready, high-resolution icns files. (You can find complete documentation for this tool by enteringman iconutil in Terminal.) Using this tool also compresses the resulting icns file, so there is no need for you to perform additional compression.
Note: Don’t use Icon Composer—it can’t create high-resolution icns files.