This article attempts to give a sort of ‘orientation tour’ for people whose previous programming background is in high (ish) level languages such as Java or Python, and who now find that they need or want to learn C.

When you resize, rotate, or in any way transform an image; or more generally when you resample some discrete signal, the software you are using must interpolate between the discrete points to produce a result. Linear and cubic interpolation are easy to explain, but Lánczos interpolation, one of the most popular methods, is more interesting. In this post we will build up to how Lánczos interpolation works, pulling in various interesting topics on the way.