I have a movie projector which is projecting an image on a brown wall. The projector allows me to adjust 6 values. Red brightness, Green brightness, Blue brightness. Red contrast, Green contrast, Blue contrast.
Is it possible to "cancel out" the color of the brown wall by adjusting the RGB values of the projector? By cancel out, I mean so that the end result of the projected image is equivalent, as if the wall was a more neutral gray or white.
If this is possible, is there a way to do it without an expensive colorimeter? Maybe with some image processing from a phone camera?