Get the inverse of polyshape?

When you have a polygon like:

pgon = polyshape([200 250 260 200],[230 180 250 230])

plot(pgon)

how can you get back the corners of the polygon, i.e. what is the inverse function of polyshape?

Answer 1

[Steven Lord]

Do you want to get the vertices from the polyshape object or from the plotted Polygon object?

pgon = polyshape([0 0 1 1],[1 0 0 1])

pgon = 
  polyshape with properties:

      Vertices: [4×2 double]
    NumRegions: 1
      NumHoles: 0

V = pgon.Vertices

V = 4×2

0 1 1 1 1 0 0 0

h = plot(pgon)

h = 
  Polygon with properties:

    FaceColor: [0 0.4470 0.7410]
    FaceAlpha: 0.3500
    EdgeColor: [0 0 0]
    LineWidth: 0.5000
    LineStyle: '-'
        Shape: [1×1 polyshape]

  Show all properties

V2 = h.Shape.Vertices

V2 = 4×2

0 1 1 1 1 0 0 0

Note that V and V2 may not necessarily be the same as the vectors you passed into polyshape if those original vectors specified polygonal regions with collinear points, intersections, or improper nesting. See the "Area of Bow Tie" example on the documentation page for polyshape.

B = polyshape([0 0; 1 1; 1 0; 0 1; 0 0]);

Warning: Polyshape has duplicate vertices, intersections, or other inconsistencies that may produce inaccurate or unexpected results. Input data has been modified to create a well-defined polyshape.

V3 = B.Vertices

V3 = 7×2

0 0 0 1.0000 0.5000 0.5000 NaN NaN 1.0000 1.0000 1.0000 0 0.5000 0.5000