Color Perception and Correcting for Chromatic Induction

Research by Evan McLain, Corin Anderson, David Salesin, and Dani Lischinski

In human vision, the perceived color of an object does not depend solely upon the physical light that leaves the surface of that object. Many other factors play a role in the perceived color, including the color and brightness of surrounding objects. This is most clearly noted in the image below:

[Image of obvious color shifts]

Believe it or not, the two center gray boxes are the same color, although they clearly do not appear to be so. This is due to chromatic induction (actually, it is brightness induction, but that subtly doesn't matter a whole lot here). Automatically correcting (i.e. removing) this effect is the topic of our research.

As motivation for this research, consider the case where the image below were your company logo:

[Image of gray company logo]

If you were to compose your logo with the image below on the left, you would generate an image like that shown below and on the right:

[Green field on top, yellow field on bottom] [Composite image:  gray logo looks red on top, blue on bottom]

This is an undesireable effect -- your company logo is supposed to be all gray, not red on top, green on bottom, and blue on the side! So you must somehow correct this problem.

One method of correction is simple avoidance: never put your company logo on any strongly colored backgrounds. The problem with this solution is that you are now restricted with what you can do with your company's logo. The second solution is to hand-correct your company's logo. That is, with the knowledge that the top of your logo will become reddish, you could add green to your logo, and balance the chromatic induction. While this solution works for simple cases such as the one above, consider, the case below, where the background color changes widely and smoothly. It would be difficult to guess what the resulting induced effects would be:

[Logo on mottled  background with
smooth color transitions]

The third alternative is to have a computer automatically correct for chromatic induction, letting you have complete freedom of design with your company's logo. This is what our research is doing. Our goal is to design a program whose input is the graphic artist's image, where colors are specified by what color should be perceived at each point. The program would compute how the design elements will interact with each other by chromatic and brightness induction, and adjust the image accordingly. The output would be an image whose physical colors may be different than the input's, but whose perceived colors would be what the graphic artist specified.
Last updated June 10th, 1996