Merge #537

537: Don't panic on negative epsilon r=frewsxcv a=urschrei

Fixes #536

Co-authored-by: Stephan Hügel <shugel@tcd.ie>

geo/src/algorithm/simplify.rs

@@ -19,6 +19,10 @@ fn rdp<T>(points: &[Point<T>], epsilon: &T) -> Vec<Point<T>>
 where
     T: Float,
 {
+    // Epsilon must be greater than zero for any meaningful simplification to happen
+    if *epsilon <= T::zero() {
+        points.to_vec();
+    }
     compute_rdp(
         &points
             .into_iter()
@@ -87,6 +91,8 @@ where
 /// rings. This may result in invalid Polygons, and has no guarantee of preserving topology.
 ///
 /// Multi* objects are simplified by simplifing all their constituent geometries individually.
+///
+/// An epsilon less than or equal to zero will return an unaltered version of the geometry.
 pub trait Simplify<T, Epsilon = T> {
     /// Returns the simplified representation of a geometry, using the [Ramer–Douglas–Peucker](https://en.wikipedia.org/wiki/Ramer–Douglas–Peucker_algorithm) algorithm
     ///
@@ -124,6 +130,8 @@ pub trait Simplify<T, Epsilon = T> {
 ///
 /// This operation uses the [Ramer–Douglas–Peucker algorithm](https://en.wikipedia.org/wiki/Ramer–Douglas–Peucker_algorithm)
 /// and does not guarantee that the returned geometry is valid.
+///
+/// An epsilon less than or equal to zero will return an unaltered version of the geometry.
 pub trait SimplifyIdx<T, Epsilon = T> {
     /// Returns the simplified indices of a geometry, using the [Ramer–Douglas–Peucker](https://en.wikipedia.org/wiki/Ramer–Douglas–Peucker_algorithm) algorithm
     ///

geo/src/algorithm/simplifyvw.rs

@@ -191,6 +191,10 @@ fn visvalingam<T>(orig: &LineString<T>, epsilon: &T) -> Vec<Coordinate<T>>
 where
     T: Float,
 {
+    // Epsilon must be greater than zero for any meaningful simplification to happen
+    if *epsilon <= T::zero() {
+        return orig.0.to_vec()
+    }
     let subset = visvalingam_indices(orig, epsilon);
     // filter orig using the indices
     // using get would be more robust here, but the input subset is guaranteed to be valid in this case
@@ -251,7 +255,7 @@ fn visvalingam_preserve<T>(
 where
     T: Float + RTreeNum,
 {
-    if orig.0.len() < 3 {
+    if orig.0.len() < 3 || *epsilon <= T::zero() {
         return orig.0.to_vec();
     }
     let max = orig.0.len();
@@ -425,6 +429,8 @@ where
 /// Polygons are simplified by running the algorithm on all their constituent rings.  This may
 /// result in invalid Polygons, and has no guarantee of preserving topology. Multi* objects are
 /// simplified by simplifying all their constituent geometries individually.
+///
+/// An epsilon less than or equal to zero will return an unaltered version of the geometry.
 pub trait SimplifyVW<T, Epsilon = T> {
     /// Returns the simplified representation of a geometry, using the [Visvalingam-Whyatt](http://www.tandfonline.com/doi/abs/10.1179/000870493786962263) algorithm
     ///
@@ -463,6 +469,8 @@ pub trait SimplifyVW<T, Epsilon = T> {
 ///
 /// This operation uses the Visvalingam-Whyatt algorithm,
 /// and does **not** guarantee that the returned geometry is valid.
+///
+/// An epsilon less than or equal to zero will return an unaltered version of the geometry.
 pub trait SimplifyVwIdx<T, Epsilon = T> {
     /// Returns the simplified representation of a geometry, using the [Visvalingam-Whyatt](http://www.tandfonline.com/doi/abs/10.1179/000870493786962263) algorithm
     ///
@@ -498,6 +506,8 @@ pub trait SimplifyVwIdx<T, Epsilon = T> {
 }
 
 /// Simplifies a geometry, preserving its topology by removing self-intersections
+///
+/// An epsilon less than or equal to zero will return an unaltered version of the geometry.
 pub trait SimplifyVWPreserve<T, Epsilon = T> {
     /// Returns the simplified representation of a geometry, using a topology-preserving variant of the
     /// [Visvalingam-Whyatt](http://www.tandfonline.com/doi/abs/10.1179/000870493786962263) algorithm.