Declaration

TBilinearGradientSampler = class(TCustomSparsePointGradientSampler)

Description

A sparse point gradient interpolator using a inverse bilinear interpolation.

Based on four (and only four) vertices, with each vertex specified with a certain color, an inverse bilinear interpolation of color is calculated. Outside this the colours extends as before, but discontinuities may occur.

Mathematics & Algorithm

Given 4 vertex coordinates $P_{00},P_{10},P_{01},P_{11}$ and colors $C_{00},C_{10},C_{01},C_{11}$, sampling coordinates $(u,v)\in [0,1]\times [0,1]$ parameterize the unit quad:

$$P(u,v)=(1-u)(1-v)P_{00}+u(1-v)P_{10}+(1-u)v{P}_{01}+uv{P}_{11}$$$$C(u,v)=(1-u)(1-v)C_{00}+u(1-v)C_{10}+(1-u)v{C}_{01}+uv{C}_{11}$$

References

• Bilinear Interpolation - Wikipedia