Figure 3: Superposition on four-channel color mixing
The method described here is easily expandable to more than four LED colors. In Figure 3
, the four triangles are made up of the following LED triplets: TR1(R,G,B), TR2(R,A,B), TR3(R,G,A), and TR4(G,A,B).
Each triangle is solved for dimming values using three-channel color mixing functions. Out of these four triangles two give all non negative dimming values and two have one or all dimming values negative. Triangles with any or all negatives values are not valid and are discarded. Dimming arrays with all positive values are accumulated. The interpretation of negative dimming values is that the desired point lies outside the triangle formed by three basic colors. For example, in Figure 4
, RGB triangle returns all non negative values for P1; for P2, at least one dimming value is negative.
Two positive dimming values for each desired color are added and scaled appropriately. A negative dimming value implies that the desired color is not inside the gamut so that cannot be generated using the particular base colors.
Figure 4: Positive and negative dimming values