geo-validity-check

Expose a Valid trait to check if rust geo-types geometries are valid.

Valid trait has the following signature:

trait Valid {
    fn is_valid(&self) -> bool;
    fn explain_invalidity(&self) -> Option<ProblemReport>;
}

The result of the invalidity reason is provided in a ProblemReport struct (it contains a Vec of (Problem, ProblemPosition), two enums that respectively represent the type of problem and the position of the problem in the tested geometry - having this machine-readable information could be useful to try to fix the geometry). This ProblemReport result can also be formatted as a string as it implements the Display trait.

Checks implemented

• Coord and Point use finite numbers
• MultiPoint is made of valid points
• Rect, Line and Triangle are made of valid coords
• Triangle are not empty or degenerate (i.e. all points are different and not collinear)
• Line is not of 0-length (i.e. both points are not the same)
• LineString is made of valid points
• LineString is not empty
• LineString has at least two different points
• MultiLineString is made of valid linestrings
• Polygon rings are made of valid points
• Polygon rings have at least 4 points (including the closing point)
• Polygon interior rings are contained in the exterior ring (but can touch it on a point)
• Polygon interior rings don't cross each other (but can touch on a point)
• MultiPolygon components don't cross each other (but can touch on a point)
• MultiPolygon is made of valid polygons
• GeometryCollection is made of valid geometries

Verification is done against GEOS (any geometry invalid according to GEOS should be invalid according to this crate - the inverse doesn't have to be true since we are doing some extra check).

Example

use geo_validity_check::Valid;
use geo_types::{Point, LineString, Polygon, MultiPolygon};

let line1 = LineString::from(vec![(0., 0.), (1., 1.)]);
let line2 = LineString::from(vec![(0., 0.), (0., 0.)]);
let line3 = LineString::from(vec![(0., 0.), (f64::NAN, f64::NAN), (1., 1.)]);

assert!(line1.is_valid());
assert!(!line2.is_valid());
assert!(!line3.is_valid());

println!("{}", line2.invalidity_reason().unwrap()); // "LineString has too few points at coordinate 0 of the LineString"
println!("{}", line3.invalidity_reason().unwrap()); // "Coordinate is not finite (NaN or infinite) at coordinate 1 of the LineString"

let polygon = Polygon::new(
    LineString::from(vec![(0.5, 0.5), (3., 0.5), (3., 2.5), (0.5, 2.5), (0.5, 0.5)]),
    vec![LineString::from(vec![(1., 1.), (1., 2.), (2.5, 2.), (3.5, 1.), (1., 1.)])],
);

assert!(!polygon.is_valid());
println!("{}", polygon.invalidity_reason().unwrap()); // "The interior ring of a Polygon is not contained in the exterior ring on the interior ring n°0"

let multipolygon = MultiPolygon(vec![
    Polygon::new(
        LineString::from(vec![(0.5, 0.5), (3., 0.5), (3., 2.5), (0.5, 2.5), (0.5, 0.5)]),
        vec![LineString::from(vec![(1., 1.), (1., 2.), (2.5, 2.), (3.5, 1.), (1., 1.)])],
    ),
    Polygon::new(
        LineString::from(vec![(0.5, 0.5), (3., 0.5), (3., 2.5), (0.5, 2.5), (0.5, 0.5)]),
        vec![LineString::from(vec![(1., 1.), (1., 2.), (2.5, 2.), (3.5, 1.), (1., 1.)])],
    ),
]);

assert!(!multipolygon.is_valid());
println!("{}", multipolygon.invalidity_reason().unwrap());
// "The interior ring of a Polygon is not contained in the exterior ring on the interior ring n°0 of the Polygon n°0 of the MultiPolygon
// Two Polygons of MultiPolygons are identical on the exterior ring of the Polygon n°0 of the MultiPolygon
// The interior ring of a Polygon is not contained in the exterior ring on the interior ring n°0 of the Polygon n°1 of the MultiPolygon
// Two Polygons of MultiPolygons are identical on the exterior ring of the Polygon n°1 of the MultiPolygon"

TODO / Ideas

• Improve the description of the invalidity reason (e.g. "Interior ring 0 intersects the exterior ring" could be "Interior ring 0 intersects the exterior ring at point (1.5, 1.5)")

• Add a make_valid or fix_invalidity method to try to fix the geometry (e.g. by removing the invalid points ?)

• Return the first invalidity reason found (instead of all of them) in invalidity_reason method ? (because some other checks could fail because of the first invalidity reason)

• Implement a rule that states that a Polygon is valid if the polygon interior is simply connected (i.e. the rings must not touch in a way that splits the polygon into more than one part) ?

License

Licensed under either of

• Apache License, Version 2.0, (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.