Apple’s .icns format has one official tool, iconutil, which runs
only on macOS, resists scripting, and wants a rigid folder of pre-sized
PNGs. icnsify replaces it with one command that runs anywhere:
brew install jackmordaunt/tap/icnsify
icnsify -i logo.png -o Icon.icns
It takes a single image, produces every size the format wants, converts
common formats on the way in, and pipes like a Unix tool. A small GUI
previews an .icns on any operating system.
Where it is used
Fyne and Wails generate their icons with it when building macOS applications from Linux and Windows. I wrote the first version in a café in Sweden in 2018 as my first serious open-source release, from the format specification and public documentation, and it has been maintained since.
What it stands for
Minimal dependencies, instant startup, a small binary, and a task that was awkward made ordinary. The library behind it is icns, with a Rust port, icns-rs.