contour approximation

Replacing a dense boundary trace with a small set of vertices that reproduce its shape within a tolerance.

Contour approximation replaces a shape's dense, pixel-by-pixel boundary trace with a small vertex set that reproduces the same shape within a chosen tolerance $\varepsilon$ -- the Douglas-Peucker algorithm being the standard approach, recursively keeping only the points whose perpendicular distance from the current simplified line exceeds $\varepsilon$ .

Examples

Simplifying a traced coastline with $\varepsilon=5$ pixels keeps only the vertices where the boundary deviates by more than 5 pixels from a straight line between its neighbors.