  Homographies -- a mathematical formalism for relating image points across
different camera viewpoints -- are at the foundations of geometric methods in
computer vision and are used in geometric camera calibration, image
registration, and stereo vision and other tasks. In this paper, we show the
surprising result that colors across a change in viewing condition (changing
light color, shading and camera) are also related by a homography. We propose a
new color correction method based on color homography. Experiments demonstrate
that solving the color homography problem leads to more accurate calibration.
