Patent ID: 8081798

Claim:
A method in a computer system for detecting polygon boundaries of structures in an image, comprising: receiving an image; detecting in said image a set of polygon corners each substantially matching one of n corner models of an n-sided polygon model based on directions of gradients in pixel gray-values of said image; initializing tracking of polygon boundaries by selecting pairs of corners from the set of detected polygon corners which match the first 0 th and last (n−1) th corners models of the n-sided polygon model, wherein each selected pair defines a first 0 th side of a corresponding one of the polygon boundaries; using a particle filter performing Sequential Monte Carlo sampling to track intermediate sides of the polygon boundaries after the first 0 th side up to and including a penultimate (n−2) th side, wherein the particles used in the particle filter characterize the states of the polygon boundary sides, and observations used in the particle filter characterize the match similarity between the set of detected polygon corners at locations and orientations predicted by the polygon model; terminating tracking of the polygon boundaries by determining the last (n−1) th sides thereof based on specified states of the sides of the polygon boundaries for the previous n−1 sides; and blending multiple particle tracks for the same polygon into a single boundary based on importance weights that reflect particle fitness, to produce an array of polygon matches detected in said image.