convexityDefects

geometryfunctionOpenCV 5.0.0

import { convexityDefects } from '@banou/opencv-wasm'

Use after await initOpenCV(). See the initialization and named imports guide.

Explore visually: Convex hulls and defects →

Wrap a point set in its smallest convex boundary and measure inward deviations.

VISUAL WALKTHROUGHShape

REFERENCE INPUTShape with a concavity

The inward notch distinguishes the original boundary from its convex hull.

→

RESULTOuter convex envelope

For convexity defects, compare the original contour with hull edges.

Illustrative example. The stages explain the method; they are not a live OpenCV execution.

Finds the convexity defects of a contour.

The figure below displays convexity defects of a hand contour:

convexityDefects(contour: Mat, convexhull: Mat, convexityDefects: Mat): void;

contour

Input contour.

convexhull

Convex hull obtained using convexHull that should contain indices of the contour points that make the hull.

convexityDefects

Output destination, filled by the native operation. The output vector of convexity defects. In C++ and the new Python/Java interface each convexity defect is represented as 4-element integer vector (a.k.a. #Vec4i): (start_index, end_index, farthest_pt_index, fixpt_depth), where indices are 0-based indices in the original contour of the convexity defect beginning, end and the farthest point, and fixpt_depth is fixed-point approximation (with 8 fractional bits) of the distance between the farthest contour point and the hull. That is, to get the floating-point value of the depth will be fixpt_depth/256.0.

Upstream declaration ↗

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