Finds the convexity defects of a contour

defects = cv.convexityDefects(contour, convexhull)

Input

• contour Input contour. 2D point set, stored in numeric array (Nx2/Nx1x2/1xNx2) or cell array of 2-element vectors ({[x,y], ...}).
• convexhull Corresponding convex hull obtained using cv.convexHull that should contain indices of the contour points that make the hull. A numeric vector of 0-based indices.

Output

• defects The output vector of convexity defects {[v0,v1,v2,v3], ...}. Each convexity defect is represented as 4-element integer vector [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.