is.convex(x)"owin").TRUE if x is convex.x is a rectangle, the result is TRUE. If x is polygonal, the result is TRUE if x consists of a
single polygon and this polygon is equal to the minimal convex hull
of its vertices computed by chull.
If x is a mask, the algorithm first extracts all boundary
pixels of x using vertices. Then it computes
the (polygonal) convex hull $K$ of the boundary pixels.
The result is TRUE if every boundary pixel lies within
one pixel diameter of an edge of $K$.
owin,
convexhull.xy,
vertices