In mathematics, bilinear interpolation is an extension of linear interpolation for interpolating functions of two variables (e.g., and ) on a regular 2D grid. The interpolated function should not use the term of or, but, which is the bilinear form of and .
The key idea is to perform linear interpolation first in one direction, and then again in the other direction. Although each step is linear in the sampled values and in the position, the interpolation as a whole is not linear but rather quadratic in the sample location (details below).
Read more about Bilinear Interpolation: Algorithm, Application in Image Processing