use crate::{GeoNum, MultiPolygon, Polygon};
use crate::winding_order::{Winding, WindingOrder};
pub trait Orient {
/// Orients a Polygon's exterior and interior rings according to convention
///
/// By default, the exterior ring of a Polygon is oriented counter-clockwise, and any interior
/// rings are oriented clockwise.
///
/// # Examples
///
/// ```
/// use geo::orient::{Direction, Orient};
/// use geo::polygon;
///
/// // a diamond shape
/// let polygon = polygon![
/// // exterior oriented clockwise
/// exterior: [
/// (x: 1.0, y: 0.0),
/// (x: 0.0, y: 1.0),
/// (x: 1.0, y: 2.0),
/// (x: 2.0, y: 1.0),
/// (x: 1.0, y: 0.0),
/// ],
/// // interior oriented counter-clockwise
/// interiors: [
/// [
/// (x: 1.0, y: 0.5),
/// (x: 1.5, y: 1.0),
/// (x: 1.0, y: 1.5),
/// (x: 0.5, y: 1.0),
/// (x: 1.0, y: 0.5),
/// ],
/// ],
/// ];
///
/// let oriented = polygon.orient(Direction::Default);
///
/// // a diamond shape
/// let expected = polygon![
/// // exterior oriented counter-clockwise
/// exterior: [
/// (x: 1.0, y: 0.0),
/// (x: 2.0, y: 1.0),
/// (x: 1.0, y: 2.0),
/// (x: 0.0, y: 1.0),
/// (x: 1.0, y: 0.0),
/// ],
/// // interior oriented clockwise
/// interiors: [
/// [
/// (x: 1.0, y: 0.5),
/// (x: 0.5, y: 1.0),
/// (x: 1.0, y: 1.5),
/// (x: 1.5, y: 1.0),
/// (x: 1.0, y: 0.5),
/// ],
/// ],
/// ];
///
/// assert_eq!(expected, oriented);
/// ```
fn orient(&self, orientation: Direction) -> Self;
}
impl<T> Orient for Polygon<T>
where
T: GeoNum,
{
fn orient(&self, direction: Direction) -> Polygon<T> {
orient(self, direction)
}
}
impl<T> Orient for MultiPolygon<T>
where
T: GeoNum,
{
fn orient(&self, direction: Direction) -> MultiPolygon<T> {
MultiPolygon::new(self.iter().map(|poly| poly.orient(direction)).collect())
}
}
/// By default, a properly-oriented Polygon has its outer ring oriented counter-clockwise,
/// and its inner ring(s) oriented clockwise. Selecting `Reversed` will result in a Polygon
/// with a clockwise-oriented exterior ring, and counter-clockwise interior ring(s)
#[derive(Copy, Clone, Debug)]
pub enum Direction {
/// exterior ring is oriented counter-clockwise, interior rings are oriented clockwise
Default,
/// exterior ring is oriented clockwise, interior rings are oriented counter-clockwise
Reversed,
}
// orient a Polygon according to convention
// by default, the exterior ring will be oriented ccw
// and the interior ring(s) will be oriented clockwise
fn orient<T>(poly: &Polygon<T>, direction: Direction) -> Polygon<T>
where
T: GeoNum,
{
let interiors = poly
.interiors()
.iter()
.map(|l| {
l.clone_to_winding_order(match direction {
Direction::Default => WindingOrder::Clockwise,
Direction::Reversed => WindingOrder::CounterClockwise,
})
})
.collect();
let ext_ring = poly.exterior().clone_to_winding_order(match direction {
Direction::Default => WindingOrder::CounterClockwise,
Direction::Reversed => WindingOrder::Clockwise,
});
Polygon::new(ext_ring, interiors)
}
#[cfg(test)]
mod test {
use super::*;
use crate::{LineString, Polygon};
#[test]
fn test_polygon_orientation() {
// a diamond shape, oriented clockwise outside
let points_ext = vec![(1.0, 0.0), (0.0, 1.0), (1.0, 2.0), (2.0, 1.0), (1.0, 0.0)];
// counter-clockwise interior
let points_int = vec![(1.0, 0.5), (1.5, 1.0), (1.0, 1.5), (0.5, 1.0), (1.0, 0.5)];
let poly1 = Polygon::new(
LineString::from(points_ext),
vec![LineString::from(points_int)],
);
// a diamond shape, oriented counter-clockwise outside,
let oriented_ext = vec![(1.0, 0.0), (2.0, 1.0), (1.0, 2.0), (0.0, 1.0), (1.0, 0.0)];
let oriented_ext_ls = LineString::from(oriented_ext);
// clockwise interior
let oriented_int_raw = vec![(1.0, 0.5), (0.5, 1.0), (1.0, 1.5), (1.5, 1.0), (1.0, 0.5)];
let oriented_int_ls = LineString::from(oriented_int_raw);
// build corrected Polygon
let oriented = orient(&poly1, Direction::Default);
assert_eq!(oriented.exterior().0, oriented_ext_ls.0);
assert_eq!(oriented.interiors()[0].0, oriented_int_ls.0);
}
}