Glossary

The 7 words this book marks with a wavy underline. Each one also appears on hover where it is used, so this page is for looking one up, or for finding the chapter that needed it.

Antialiased: Softened at the edges. A diagonal drawn on a grid of square pixels is faded across the boundary ones so it reads as a line rather than as a staircase.
Centroid: The average position of a set of points, which is to say the shape's balance point.
Congruent: The same shape and the same size, allowing for having been turned or moved. Two icons are congruent when one could be laid exactly over the other without stretching it.
Interpolate: To produce the in-between values. Given a start and an end, interpolating at the halfway point gives you the value halfway between them.
Parameterisation: How a curve's points are spaced out along it as you sweep from one end to the other. Two curves can draw the same line and still be travelled at different speeds.
Procrustes: A standard way of finding the single rotation, scale and shift that best lays one set of points over another. Named, grimly, after the Greek innkeeper who made guests fit the bed.
Residual: What is left over after the closest possible fit. Zero means the two shapes matched exactly, and a bigger number means the fit had to give something up to get there.