/// <summary>
/// Computes the difference between the specified <see cref="IGeometry" /> instances.
/// </summary>
/// <param name="geometry">The geometry.</param>
/// <param name="otherGeometry">The other geometry.</param>
/// <returns>The difference between the <see cref="IGeometry" /> instances.</returns>
/// <exception cref="System.ArgumentNullException">
/// The geometry is null.
/// or
/// The other geometry is null.
/// </exception>
/// <exception cref="System.ArgumentException">The operation is not supported with the specified geometry types.</exception>
public static IGeometry Difference(this IGeometry geometry, IGeometry otherGeometry)
{
if (geometry == null)
{
throw new ArgumentNullException("geometry", "The geometry is null.");
}
if (otherGeometry == null)
{
throw new ArgumentNullException("otherGeometry", "The other geometry is null.");
}
using (IGeometryOverlayOperator op = GetOverlayOperator(geometry))
{
return(op.Difference(geometry, otherGeometry));
}
}
public void HalfedgeGeometryOverlayTest()
{
IMultiPolygon first = _factory.CreateMultiPolygon(new[]
{
_factory.CreatePolygon(
_factory.CreatePoint(0, 0),
_factory.CreatePoint(10, 0),
_factory.CreatePoint(10, 10),
_factory.CreatePoint(0, 10)),
_factory.CreatePolygon(
_factory.CreatePoint(10, 0),
_factory.CreatePoint(20, 0),
_factory.CreatePoint(20, 10),
_factory.CreatePoint(10, 10)),
_factory.CreatePolygon(
_factory.CreatePoint(0, 10),
_factory.CreatePoint(10, 10),
_factory.CreatePoint(10, 20),
_factory.CreatePoint(0, 20)),
});
IMultiPolygon second = _factory.CreateMultiPolygon(new[]
{
_factory.CreatePolygon(
_factory.CreatePoint(-5, -5),
_factory.CreatePoint(5, -5),
_factory.CreatePoint(5, 5),
_factory.CreatePoint(-5, 5)),
_factory.CreatePolygon(
_factory.CreatePoint(5, -5),
_factory.CreatePoint(15, -5),
_factory.CreatePoint(15, 5),
_factory.CreatePoint(5, 5)),
_factory.CreatePolygon(
_factory.CreatePoint(-5, -15),
_factory.CreatePoint(5, -15),
_factory.CreatePoint(5, -5),
_factory.CreatePoint(-5, -5)),
});
Coordinate[][] expected = new[]
{
// ExternalFirst
new[]
{
new Coordinate(0, 10),
new Coordinate(10, 10),
new Coordinate(10, 20),
new Coordinate(0, 20),
new Coordinate(0, 10)
},
new[]
{
new Coordinate(0, 5),
new Coordinate(5, 5),
new Coordinate(10, 5),
new Coordinate(10, 10),
new Coordinate(0, 10),
new Coordinate(0, 5)
},
new[]
{
new Coordinate(10, 5),
new Coordinate(15, 5),
new Coordinate(15, 0),
new Coordinate(20, 0),
new Coordinate(20, 10),
new Coordinate(10, 10),
new Coordinate(10, 5)
},
// Internal
new[]
{
new Coordinate(5, 0),
new Coordinate(10, 0),
new Coordinate(10, 5),
new Coordinate(5, 5),
new Coordinate(5, 0)
},
new[]
{
new Coordinate(10, 0),
new Coordinate(15, 0),
new Coordinate(15, 5),
new Coordinate(10, 5),
new Coordinate(10, 0)
},
new[]
{
new Coordinate(0, 0),
new Coordinate(5, 0),
new Coordinate(5, 5),
new Coordinate(0, 5),
new Coordinate(0, 0)
},
// ExternalSecond
new[]
{
new Coordinate(-5, -15),
new Coordinate(5, -15),
new Coordinate(5, -5),
new Coordinate(-5, -5),
new Coordinate(-5, -15)
},
new[]
{
new Coordinate(-5, -5),
new Coordinate(5, -5),
new Coordinate(5, 0),
new Coordinate(0, 0),
new Coordinate(0, 5),
new Coordinate(-5, 5),
new Coordinate(-5, -5)
},
new[]
{
new Coordinate(5, -5),
new Coordinate(15, -5),
new Coordinate(15, 0),
new Coordinate(10, 0),
new Coordinate(5, 0),
new Coordinate(5, -5)
}
};
// Difference
IGeometry result = _operator.Difference(first, second);
Assert.IsInstanceOf <IGeometryCollection <IPolygon> >(result);
IGeometryCollection <IPolygon> collection = (IGeometryCollection <IPolygon>)result;
Assert.AreEqual(new[]
{
expected[0],
expected[1],
expected[2],
}.ToRingSet(), collection.Select(polygon => polygon.Shell).ToRingSet());
// Intersection
result = _operator.Intersection(first, second);
Assert.IsInstanceOf <IGeometryCollection <IPolygon> >(result);
collection = (IGeometryCollection <IPolygon>)result;
Assert.AreEqual(new[]
{
expected[3],
expected[4],
expected[5],
}.ToRingSet(), collection.Select(polygon => polygon.Shell).ToRingSet());
// Symmetric difference
result = _operator.SymmetricDifference(first, second);
Assert.IsInstanceOf <IGeometryCollection <IPolygon> >(result);
collection = (IGeometryCollection <IPolygon>)result;
Assert.AreEqual(new[]
{
expected[0],
expected[1],
expected[2],
expected[6],
expected[7],
expected[8],
}.ToRingSet(), collection.Select(polygon => polygon.Shell).ToRingSet());
// Union
result = _operator.Union(first, second);
Assert.IsInstanceOf <IGeometryCollection <IPolygon> >(result);
collection = (IGeometryCollection <IPolygon>)result;
Assert.AreEqual(expected.ToRingSet(), collection.Select(polygon => polygon.Shell).ToRingSet());
}
