A filled area bounded by one or more closed contours.
Every contour is filled in a single pass under the non-zero winding rule, so a
contour wound against the one enclosing it cuts a hole rather than filling
solid. That's the difference between a Region and a Vivid.Group of filled
polygons, where each polygon is filled without knowing about the others.
Since winding direction decides what's a hole, the vertex order of the contours is significant.
Example
A square with a square hole in it, the hole wound against the outside.
iex> use Vivid
...> outside = Polygon.init([Point.init(1, 1), Point.init(12, 1), Point.init(12, 12), Point.init(1, 12)])
...> inside = Polygon.init([Point.init(4, 4), Point.init(4, 9), Point.init(9, 9), Point.init(9, 4)])
...> Region.init([outside, inside])
...> |> to_string()
"@@@@@@@@@@@@@@\n" <>
"@ @\n" <>
"@ @\n" <>
"@ @\n" <>
"@ @\n" <>
"@ @@@@ @\n" <>
"@ @@@@ @\n" <>
"@ @@@@ @\n" <>
"@ @@@@ @\n" <>
"@ @\n" <>
"@ @\n" <>
"@ @\n" <>
"@ @\n" <>
"@@@@@@@@@@@@@@\n"Summary
Types
@type t() :: %Vivid.Region{contours: [Vivid.Polygon.t()]}
Functions
@spec contours(t()) :: [Vivid.Polygon.t()]
Returns the contours of region.
Example
iex> Vivid.Region.init([])
...> |> Vivid.Region.contours()
[]@spec init([Vivid.Polygon.t()]) :: t()
Initialize a region from a list of contours.
Example
The same two squares as above, but with the inner one wound the same way as the outer. Both contours now wind in the same direction, so the middle is enclosed twice rather than not at all, and it fills solid.
iex> use Vivid
...> outside = Polygon.init([Point.init(1, 1), Point.init(12, 1), Point.init(12, 12), Point.init(1, 12)])
...> inside = Polygon.init([Point.init(4, 4), Point.init(9, 4), Point.init(9, 9), Point.init(4, 9)])
...> Region.init([outside, inside])
...> |> to_string()
"@@@@@@@@@@@@@@\n" <>
"@ @\n" <>
"@ @\n" <>
"@ @\n" <>
"@ @\n" <>
"@ @\n" <>
"@ @\n" <>
"@ @\n" <>
"@ @\n" <>
"@ @\n" <>
"@ @\n" <>
"@ @\n" <>
"@ @\n" <>
"@@@@@@@@@@@@@@\n"