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use num_traits::Float;
use types::{LineString, Polygon, MultiPolygon};
pub trait Orient<T> {
/// 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.
///
/// ```
/// use geo::{Point, LineString, Polygon};
/// use geo::orient::{Orient, Direction};
/// // a diamond shape, oriented clockwise outside
/// let points_ext_raw = 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_raw = vec![(1.0, 0.5), (1.5, 1.0), (1.0, 1.5), (0.5, 1.0), (1.0, 0.5)];
/// let points_ext = points_ext_raw.iter().map(|e| Point::new(e.0, e.1)).collect::<Vec<_>>();
/// let points_int = points_int_raw.iter().map(|e| Point::new(e.0, e.1)).collect::<Vec<_>>();
/// let poly = Polygon::new(LineString(points_ext), vec![LineString(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(oriented_ext.iter().map(|e| Point::new(e.0, e.1)).collect::<Vec<_>>());
/// // clockwise interior
/// let oriented_int = 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(oriented_int.iter().map(|e| Point::new(e.0, e.1)).collect::<Vec<_>>());
/// // build corrected Polygon
/// let oriented = poly.orient(Direction::Default);
/// assert_eq!(oriented.exterior.0, oriented_ext_ls.0);
/// assert_eq!(oriented.interiors[0].0, oriented_int_ls.0);
/// ```
fn orient(&self, orientation: Direction) -> Self;
}
impl<T> Orient<T> for Polygon<T>
where T: Float
{
fn orient(&self, direction: Direction) -> Polygon<T> {
orient(self, direction)
}
}
impl<T> Orient<T> for MultiPolygon<T>
where T: Float
{
fn orient(&self, direction: Direction) -> MultiPolygon<T> {
MultiPolygon(self.0
.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,
}
// the signed area of a linear ring
fn signed_ring_area<T>(linestring: &LineString<T>) -> T
where T: Float
{
if linestring.0.is_empty() || linestring.0.len() == 1 {
return T::zero();
}
let mut tmp = T::zero();
for ps in linestring.0.windows(2) {
tmp = tmp + (ps[0].x() * ps[1].y() - ps[1].x() * ps[0].y());
}
tmp / (T::one() + T::one())
}
// 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: Float
{
let sign = match direction {
Direction::Default => T::one(),
Direction::Reversed => -T::one(),
};
let mut rings = vec![];
// process interiors first, so push and pop work
for ring in &poly.interiors {
if signed_ring_area(&ring) / sign <= T::zero() {
rings.push(LineString(ring.0.iter().cloned().collect()));
} else {
rings.push(LineString(ring.0.iter().rev().cloned().collect()));
}
}
if signed_ring_area(&poly.exterior) / sign >= T::zero() {
rings.push(LineString(poly.exterior.0.iter().cloned().collect()));
} else {
rings.push(LineString(poly.exterior.0.iter().rev().cloned().collect()));
}
Polygon::new(rings.pop().unwrap(), rings)
}
#[cfg(test)]
mod test {
use types::{Polygon, LineString, Point};
use super::*;
#[test]
fn test_polygon_orientation() {
// a diamond shape, oriented clockwise outside
let points_ext_raw = 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_raw = vec![(1.0, 0.5), (1.5, 1.0), (1.0, 1.5), (0.5, 1.0), (1.0, 0.5)];
let points_ext = points_ext_raw
.iter()
.map(|e| Point::new(e.0, e.1))
.collect::<Vec<_>>();
let points_int = points_int_raw
.iter()
.map(|e| Point::new(e.0, e.1))
.collect::<Vec<_>>();
let poly1 = Polygon::new(LineString(points_ext), vec![LineString(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(oriented_ext
.iter()
.map(|e| Point::new(e.0, e.1))
.collect::<Vec<_>>());
// 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(oriented_int_raw
.iter()
.map(|e| Point::new(e.0, e.1))
.collect::<Vec<_>>());
// 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);
}
}