Finds the convex hull of a point set

hull = cv.convexHull(points)
hull = cv.convexHull(points, 'OptionName', optionValue, ...)

Input

• points Input 2D point set, stored in numeric array (Nx2/Nx1x2/1xNx2) or cell array of 2-element vectors ({[x,y], ...}).

Output

• hull Output convex hull. It is either an integer vector of indices or vector of points. In the first case, the hull elements are 0-based indices of the convex hull points in the original array (since the set of convex hull points is a subset of the original point set). In the second case, hull elements are the convex hull points themselves. In case output is the hull points, it has the same type as the input.

Options

• ReturnPoints Operation flag. In case of a matrix, when the flag is true, the function returns convex hull points (Mx2 matrix). Otherwise, it returns indices of the convex hull points (vector of length M). In case the input is a cell-array, when the flag is true, the function return convex hull points (as a cell-array of points). Otherwise it returns indices of points (vector of length M). default true
• Clockwise Orientation flag. If it is true, the output convex hull is oriented clockwise. Otherwise, it is oriented counter-clockwise. The usual screen coordinate system is assumed so that the origin is at the top-left corner, x axis is oriented to the right, and y axis is oriented downwards. default false

The function cv.convexHull finds the convex hull of a 2D point set using the Sklansky's algorithm [Sklansky82] that has O(N logN) complexity in the current implementation. See the sample convexhull_demo.m that demonstrates the usage of the function.

References

[Sklansky82]:

Jack Sklansky. "Finding the convex hull of a simple polygon". Pattern Recognition Letters, 1(2):79-83, 1982.