Hands-On Image Processing with Python

Up-sampling and interpolation 

In order to improve the up-sampled output image quality, we can use some interpolation method such as bi-linear or bi-cubic interpolation. Let's see how.

Bi-linear interpolation

Let's consider a grayscale image, which is basically a 2D matrix of pixel values at integer grid locations. To interpolate the pixel value at any point P on the grid, the 2D analogue of linear interpolation: bilinear interpolation can be used. In this case, for each possible point P (that we would like to interpolate), four neighbors (namely, Q₁₁, Q₁₂, Q₂₂, and Q₂₁) are going to be there and the intensity values of these four neighbors are to be combined to compute the interpolated intensity at the point P, as shown in the following ...