Elephicon

Elephicon is a graphical interface for creating Apple ICNS and Microsoft ICO icon files from PNG images. It is the macOS app variant distributed by Homebrew Cask, rather than a command-line tool.

• Create both ICNS and ICO files from PNG sources.
• Use non-square PNG images as input; the project describes a 24-bit, 1024×1024 PNG with an alpha channel as ideal, while noting that other dimensions and most PNG formats can also work.
• Adjust available options from the app’s context menu.
• The project documents embedded icon sizes from 16×16 through 512×512, with the available sizes depending on whether the output is ICO or ICNS.

Install with brew install --cask elephicon. The cask installs Elephicon.app in /Applications. Elephicon requires macOS 13 or later. To get started, open the app and provide a PNG image to create an icon file. The project notes that 256×256 pixels is sufficient when creating only ICO files.

Sources: Elephicon project · Homebrew Cask entry