SOIL is a tiny C library used primarily for uploading textures into OpenGL. It is based on stb_image version 1.16, the public domain code from Sean Barrett (found here). It has been extended to load ...
Following you have an example of 3 samples (4 images (multi-spectral) of 3x3 pixeles) corresponding to class 3 (grey soil). Well, all of this seems very complicated, and the first time it was for me ...