dack is an X11 wallpaper setter that can apply filters and other effects to images during runtime.

The program is controlled using a configuration file rather than command line arguments, and the main feature is being able to apply a multitude of filters on wallpapers during runtime to create various effects.

As a simple example the desktop background can be made black and white while the source image remains unchanged.

dack can be customized via runtime configuration dack.cfg placed in ~/.config/dack/ or XDG_CONFIG_HOME equivalent.

Optionally a configuration file can be specified using the DACK_CONFIG_PATH environment variable.

A configuration file passed as a command line argument will take precedence.

More details can be found on the wiki