Fig. 9.

Using more patches for a color transformation does not guarantee increased transformation accuracy. In this example, color-transformation error is computed after 1–24 patches are used. There were many possible ways the patches could have been selected; only three are shown here. Regardless of patch ordering, overall color-transformation error is minimized after the inclusion of the 18th patch. The first six patches of orders 1 and 2 are chromatic, and for order 3, they are achromatic. The errors associated with order 3 are higher initially because the scene, which consists of a photo of an MCC, is mostly chromatic. Note that it is not possible to have the total error be identically zero even in this simple example due to numerical error and noise.