I do most of my work in either a terminal or a web browser. I prefer my terminals to use bright colours on dark. I would really prefer that web pages tended to look this way as well, but that's not under my control. The problem is that when I switch from a light-on-dark terminal to a dark-on-light web page (like this one), my eyes have to adjust to the overall rise in screen brightness. Apparently this is bad for your eyes, in addition to being painful and annoying.
It would seem to be possible for some layer of the interface to adjust the displayed colours for parts of the screen, or perhaps for particular windows, to reduce the brightness of the brighter areas of the screen. Can this be done, possibly with a Compiz extension?