How do I calculate a four colour gradient?

Question

If I have four colours (A, B, C & D) on four corners of a square and I want to fill that square with a gradient that blends nicely between the four colours how would I c

Answer 1

1. Determine the distance of point E to each point A,B,C,D

2. The color for point E will be the combination of Red / Green / Blue. Calculate each color axis as the average of the same color axis for A,B,C,D, ponderating by distance.

   distance_a = sqrt((xa-xe)^2+(ya-ye)^2)

   distance_b = ....

   sum_distances = distance_a + distance_b ...

   red = (red_adistance_a + red_bdistance_b ... ) / sum_distances

   color_E = ColorFromARgb(red,green,blue)