add DensifyHaversine trait

geo/CHANGES.md

@@ -2,6 +2,7 @@
 
 ## Unreleased
 
+* Add `DensifyHaversine` trait to densify spherical line geometry
 * Add `LineStringSegmentize` trait to split a single `LineString` into `n` `LineStrings` as a `MultiLineString`
 * Add `EuclideanDistance` implementations for all remaining geometries.
   * <https://github.com/georust/geo/pull/1029>

geo/src/algorithm/densify_haversine.rs

@@ -0,0 +1,263 @@
+use num_traits::FromPrimitive;
+
+use crate::{
+    CoordFloat, CoordsIter, Line, LineString, MultiLineString, MultiPolygon, Point, Polygon, Rect,
+    Triangle,
+};
+
+use crate::{HaversineIntermediate, HaversineLength};
+
+/// Returns a new spherical geometry containing both existing and new interpolated coordinates with
+/// a maximum distance of `max_distance` between them.
+///
+/// Note: `max_distance` must be greater than 0.
+///
+/// ## Units
+///
+/// `max_distance`: meters
+///
+/// # Examples
+/// ```
+/// use geo::{coord, Line, LineString};
+/// use geo::DensifyHaversine;
+///
+/// let line = Line::new(coord! {x: 0.0, y: 0.0}, coord! { x: 0.0, y: 1.0 });
+/// // known output
+/// let output: LineString = vec![[0.0, 0.0], [0.0, 0.5], [0.0, 1.0]].into();
+/// // densify
+/// let dense = line.densify_haversine(100000.0);
+/// assert_eq!(dense, output);
+///```
+pub trait DensifyHaversine<F: CoordFloat> {
+    type Output;
+
+    fn densify_haversine(&self, max_distance: F) -> Self::Output;
+}
+
+// Helper for densification trait
+fn densify_line<T: CoordFloat + FromPrimitive>(
+    line: Line<T>,
+    container: &mut Vec<Point<T>>,
+    max_distance: T,
+) {
+    assert!(max_distance > T::zero());
+    container.push(line.start_point());
+    let num_segments = (line.haversine_length() / max_distance)
+        .ceil()
+        .to_u64()
+        .unwrap();
+    // distance "unit" for this line segment
+    let frac = T::one() / T::from(num_segments).unwrap();
+    for segment_idx in 1..num_segments {
+        let ratio = frac * T::from(segment_idx).unwrap();
+        let start = line.start;
+        let end = line.end;
+        let interpolated_point =
+            Point::from(start).haversine_intermediate(&Point::from(end), ratio);
+        container.push(interpolated_point);
+    }
+}
+
+impl<T> DensifyHaversine<T> for MultiPolygon<T>
+where
+    T: CoordFloat + FromPrimitive,
+    Line<T>: HaversineLength<T>,
+    LineString<T>: HaversineLength<T>,
+{
+    type Output = MultiPolygon<T>;
+
+    fn densify_haversine(&self, max_distance: T) -> Self::Output {
+        MultiPolygon::new(
+            self.iter()
+                .map(|polygon| polygon.densify_haversine(max_distance))
+                .collect(),
+        )
+    }
+}
+
+impl<T> DensifyHaversine<T> for Polygon<T>
+where
+    T: CoordFloat + FromPrimitive,
+    Line<T>: HaversineLength<T>,
+    LineString<T>: HaversineLength<T>,
+{
+    type Output = Polygon<T>;
+
+    fn densify_haversine(&self, max_distance: T) -> Self::Output {
+        let densified_exterior = self.exterior().densify_haversine(max_distance);
+        let densified_interiors = self
+            .interiors()
+            .iter()
+            .map(|ring| ring.densify_haversine(max_distance))
+            .collect();
+        Polygon::new(densified_exterior, densified_interiors)
+    }
+}
+
+impl<T> DensifyHaversine<T> for MultiLineString<T>
+where
+    T: CoordFloat + FromPrimitive,
+    Line<T>: HaversineLength<T>,
+    LineString<T>: HaversineLength<T>,
+{
+    type Output = MultiLineString<T>;
+
+    fn densify_haversine(&self, max_distance: T) -> Self::Output {
+        MultiLineString::new(
+            self.iter()
+                .map(|linestring| linestring.densify_haversine(max_distance))
+                .collect(),
+        )
+    }
+}
+
+impl<T> DensifyHaversine<T> for LineString<T>
+where
+    T: CoordFloat + FromPrimitive,
+    Line<T>: HaversineLength<T>,
+    LineString<T>: HaversineLength<T>,
+{
+    type Output = LineString<T>;
+
+    fn densify_haversine(&self, max_distance: T) -> Self::Output {
+        if self.coords_count() == 0 {
+            return LineString::new(vec![]);
+        }
+
+        let mut new_line = vec![];
+        self.lines()
+            .for_each(|line| densify_line(line, &mut new_line, max_distance));
+        // we're done, push the last coordinate on to finish
+        new_line.push(self.points().last().unwrap());
+        LineString::from(new_line)
+    }
+}
+
+impl<T> DensifyHaversine<T> for Line<T>
+where
+    T: CoordFloat + FromPrimitive,
+    Line<T>: HaversineLength<T>,
+    LineString<T>: HaversineLength<T>,
+{
+    type Output = LineString<T>;
+
+    fn densify_haversine(&self, max_distance: T) -> Self::Output {
+        let mut new_line = vec![];
+        densify_line(*self, &mut new_line, max_distance);
+        // we're done, push the last coordinate on to finish
+        new_line.push(self.end_point());
+        LineString::from(new_line)
+    }
+}
+
+impl<T> DensifyHaversine<T> for Triangle<T>
+where
+    T: CoordFloat + FromPrimitive,
+    Line<T>: HaversineLength<T>,
+    LineString<T>: HaversineLength<T>,
+{
+    type Output = Polygon<T>;
+
+    fn densify_haversine(&self, max_distance: T) -> Self::Output {
+        self.to_polygon().densify_haversine(max_distance)
+    }
+}
+
+impl<T> DensifyHaversine<T> for Rect<T>
+where
+    T: CoordFloat + FromPrimitive,
+    Line<T>: HaversineLength<T>,
+    LineString<T>: HaversineLength<T>,
+{
+    type Output = Polygon<T>;
+
+    fn densify_haversine(&self, max_distance: T) -> Self::Output {
+        self.to_polygon().densify_haversine(max_distance)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::coord;
+
+    #[test]
+    fn test_polygon_densify() {
+        let exterior: LineString = vec![
+            [4.925, 45.804],
+            [4.732, 45.941],
+            [4.935, 46.513],
+            [5.821, 46.103],
+            [5.627, 45.611],
+            [5.355, 45.883],
+            [4.925, 45.804],
+        ]
+        .into();
+
+        let polygon = Polygon::new(exterior, vec![]);
+
+        let output_exterior: LineString = vec![
+            [4.925, 45.804],
+            [4.732, 45.941],
+            [4.8329711649985505, 46.2270449096239],
+            [4.935, 46.513],
+            [5.379659133344039, 46.30885540136222],
+            [5.821, 46.103],
+            [5.723570877658867, 45.85704103535437],
+            [5.627, 45.611],
+            [5.355, 45.883],
+            [4.925, 45.804],
+        ]
+        .into();
+
+        let dense = polygon.densify_haversine(50000.0);
+        assert_relative_eq!(dense.exterior(), &output_exterior);
+    }
+
+    #[test]
+    fn test_linestring_densify() {
+        let linestring: LineString = vec![
+            [-3.202, 55.9471],
+            [-3.2012, 55.9476],
+            [-3.1994, 55.9476],
+            [-3.1977, 55.9481],
+            [-3.196, 55.9483],
+            [-3.1947, 55.9487],
+            [-3.1944, 55.9488],
+            [-3.1944, 55.949],
+        ]
+        .into();
+
+        let output: LineString = vec![
+            [-3.202, 55.9471],
+            [-3.2012, 55.9476],
+            [-3.2002999999999995, 55.94760000327935],
+            [-3.1994, 55.9476],
+            [-3.1985500054877773, 55.94785000292509],
+            [-3.1977, 55.9481],
+            [-3.196, 55.9483],
+            [-3.1947, 55.9487],
+            [-3.1944, 55.9488],
+            [-3.1944, 55.949],
+        ]
+        .into();
+
+        let dense = linestring.densify_haversine(110.0);
+        assert_relative_eq!(dense, output);
+    }
+
+    #[test]
+    fn test_line_densify() {
+        let output: LineString = vec![[0.0, 0.0], [0.0, 0.5], [0.0, 1.0]].into();
+        let line = Line::new(coord! {x: 0.0, y: 0.0}, coord! { x: 0.0, y: 1.0 });
+        let dense = line.densify_haversine(100000.0);
+        assert_relative_eq!(dense, output);
+    }
+
+    #[test]
+    fn test_empty_linestring() {
+        let linestring: LineString<f64> = LineString::new(vec![]);
+        let dense = linestring.densify_haversine(10.0);
+        assert_eq!(0, dense.coords_count());
+    }
+}

geo/src/algorithm/mod.rs

@@ -80,6 +80,10 @@ pub use coords_iter::CoordsIter;
 pub mod densify;
 pub use densify::Densify;
 
+/// Densify spherical geometry components
+pub mod densify_haversine;
+pub use densify_haversine::DensifyHaversine;
+
 /// Dimensionality of a geometry and its boundary, based on OGC-SFA.
 pub mod dimensions;
 pub use dimensions::HasDimensions;

geo/src/lib.rs

@@ -154,6 +154,7 @@
 //! - **[`Centroid`](Centroid)**: Calculate the centroid of a geometry
 //! - **[`ChaikinSmoothing`](ChaikinSmoothing)**: Smoothen `LineString`, `Polygon`, `MultiLineString` and `MultiPolygon` using Chaikin's algorithm.
 //! - **[`Densify`](Densify)**: Densify linear geometry components by interpolating points
+//! - **[`DensifyHaversine`](DensifyHaversine)**: Densify spherical geometry by interpolating points on a sphere
 //! - **[`GeodesicDestination`](GeodesicDestination)**: Given a start point, bearing, and distance, calculate the destination point on a [geodesic](https://en.wikipedia.org/wiki/Geodesics_on_an_ellipsoid)
 //! - **[`GeodesicIntermediate`](GeodesicIntermediate)**: Calculate intermediate points on a [geodesic](https://en.wikipedia.org/wiki/Geodesics_on_an_ellipsoid)
 //! - **[`HaversineDestination`]**: Given a start point, bearing, and distance, calculate the destination point on a sphere