desktoppr

desktoppr is a macOS‑only command‑line utility that reads and sets the desktop picture (wallpaper). It accepts a file path to display a current image, or a file path to replace the wallpaper on one or all displays. When a folder is supplied, the tool rotates through the contained images using the system’s rotation interval, though the interval itself cannot be altered through desktoppr.

The program also provides separate commands for image scaling and background colour. Scaling can be set to fill, stretch, center, or fit, and a hex colour can be supplied for the background (note that colour changes are unsupported on macOS 14.x but work from macOS 15.4 onward). These settings apply to all screens unless a specific display index is given.

desktoppr is intended for use in scripts, managed environments, or installer packages, and can be invoked from LaunchAgents or other automation tools. The README advises inserting short delays between successive calls to ensure the wallpaper service processes each change.