manage opacity property of windows, extended version
transset-df is a heavily patched version of xorg's transset. It is used to set the transparency of windows in X with the xcomposite extension. It adds several command line options to make it easier to use directly, bound to hot keys in your window manager, or through scripts. These include the ability to select a window by window ID.
Homepage: http://www.forchheimer.se/transset-df/