ijguih987 I use an image viewer called Comic Reader, it has a gamma adjust setting. The main thing I like about the program is that pretty much every feature has an associated keyboard shortcut, including this one (ctrl+g). Although you have to have set the slider in the settings first, which of course I have; the shortcut is just a toggle. Pretty sure the program is freeware, but with such a generic name it might be a nightmare to actually find it, and I can't promise it'll work on all devices. I would think that something similar should be available for whatever you're using, though. It's possible the image viewer you're using has gamma adjust in its setting and you just haven't thought to look at those closely.