/// <summary>
/// Computes a union operation on
/// the given geometry, with the supplied precision model.
/// <para/>
/// The input must be a valid geometry.
/// Collections must be homogeneous.
/// <para/>
/// To union an overlapping set of polygons in a more performant way use <see cref="UnaryUnionNG"/>.
/// To union a polygonal coverage or linear network in a more performant way,
/// use <see cref="CoverageUnion"/>.
/// </summary>
/// <param name="geom">The geometry</param>
/// <param name="pm">The precision model to use</param>
/// <returns>The result of the union operation</returns>
/// <seealso cref="OverlayMixedPoints"/>
internal static Geometry Union(Geometry geom, PrecisionModel pm)
{
var ov = new OverlayNG(geom, null, pm, SpatialFunction.Union);
var geomOv = ov.GetResult();
return(geomOv);
}
/// <summary>
/// Reduces the precision of a geometry by rounding and snapping it to the
/// supplied <see cref="PrecisionModel"/>.<br/>
/// The input geometry must be polygonal or linear.
/// <para/>
/// The output is always a valid geometry. This implies that input components
/// may be merged if they are closer than the grid precision.
/// if merging is not desired, then the individual geometry components
/// should be processed separately.
/// <para/>
/// The output is fully noded (i.e. coincident lines are merged and noded).
/// This provides an effective way to node / snap-round a collection of <see cref="LineString"/>s.
/// </summary>
/// <param name="geom">The geometry to reduce</param>
/// <param name="pm">The precision model to use</param>
/// <returns>The precision-reduced geometry</returns>
public static Geometry ReducePrecision(Geometry geom, PrecisionModel pm)
{
if (geom == null)
{
throw new ArgumentNullException(nameof(geom));
}
var ov = new OverlayNG(geom, null, pm, SpatialFunction.Union);
/*
* Ensure reducing a area only produces polygonal result.
* (I.e. collapse lines are not output)
*/
if (geom.Dimension == Dimension.Surface)
{
ov.AreaResultOnly = true;
}
try
{
var reduced = ov.GetResult();
return(reduced);
}
catch (TopologyException ex)
{
throw new ArgumentException("Reduction failed, possible invalid input", ex);
}
}
/// <summary>
/// Computes an overlay operation for
/// the given geometry operands, with the
/// noding strategy determined by the precision model.
/// </summary>
/// <param name="geom0">The first geometry argument</param>
/// <param name="geom1">The second geometry argument</param>
/// <param name="opCode">The code for the desired overlay operation</param>
/// <param name="pm">The precision model to use</param>
/// <returns>The result of the overlay operation</returns>
public static Geometry Overlay(Geometry geom0, Geometry geom1,
SpatialFunction opCode, PrecisionModel pm)
{
var ov = new OverlayNG(geom0, geom1, pm, opCode);
var geomOv = ov.GetResult();
return(geomOv);
}
/// <summary>
/// Computes a union of a single geometry using a custom noder.
/// <para/>
/// The primary use of this is to support coverage union.
/// Because of this the overlay is performed using strict mode.
/// </summary>
/// <param name="geom">The geometry to union</param>
/// <param name="pm">The precision model to use (maybe be <c>null</c>)</param>
/// <param name="noder">The noder to use</param>
/// <returns>the result geometry</returns>
/// <seealso cref="CoverageUnion"/>
internal static Geometry Union(Geometry geom, PrecisionModel pm, INoder noder)
{
var ov = new OverlayNG(geom, null, pm, SpatialFunction.Union);
ov.Noder = noder;
ov.StrictMode = true;
var geomOv = ov.GetResult();
return(geomOv);
}
/// <summary>
/// Computes an overlay operation on the given geometry operands,
/// using a supplied <see cref="INoder"/>.
/// </summary>
/// <param name="geom0">The first geometry argument</param>
/// <param name="geom1">The second geometry argument</param>
/// <param name="opCode">The code for the desired overlay operation</param>
/// <param name="noder">The noder to use</param>
/// <returns>The result of the overlay operation</returns>
public static Geometry Overlay(Geometry geom0, Geometry geom1,
SpatialFunction opCode, INoder noder)
{
var ov = new OverlayNG(geom0, geom1, null, opCode);
ov.Noder = noder;
var geomOv = ov.GetResult();
return(geomOv);
}
/// <summary>
/// Self-snaps a geometry by running a union operation with it as the only input.
/// This helps to remove narrow spike/gore artifacts to simplify the geometry,
/// which improves robustness.
/// Collapsed artifacts are removed from the result to allow using
/// it in further overlay operations.
/// </summary>
/// <param name="geom">Geometry to self-snap</param>
/// <param name="snapTol">Snap tolerance</param>
/// <returns>The snapped geometry (homogenous)</returns>
private static Geometry SnapSelf(Geometry geom, double snapTol)
{
var ov = new OverlayNG(geom, null);
var snapNoder = new SnappingNoder(snapTol);
ov.Noder = snapNoder;
/*
* Ensure the result is not mixed-dimension,
* since it will be used in further overlay computation.
* It may however be lower dimension, if it collapses completely due to snapping.
*/
ov.StrictMode = true;
return(ov.GetResult());
}
/// <summary>
/// Computes an overlay operation on
/// the given geometry operands,
/// using the precision model of the geometry.
/// and an appropriate noder.
/// <para/>
/// The noder is chosen according to the precision model specified.
/// <list type="bullet">
/// <item><description>For <see cref="PrecisionModels.Fixed"/>
/// a snap-rounding noder is used, and the computation is robust.</description></item>
/// <item><description>For <see cref="PrecisionModels.Floating"/>
/// a non-snapping noder is used,
/// and this computation may not be robust.
/// If errors occur a <see cref="TopologyException"/> is thrown.</description></item>
/// </list>
/// </summary>
/// <param name="geom0">The first geometry argument</param>
/// <param name="geom1">The second geometry argument</param>
/// <param name="opCode">The code for the desired overlay operation</param>
/// <returns>The result of the overlay operation</returns>
public static Geometry Overlay(Geometry geom0, Geometry geom1, SpatialFunction opCode)
{
var ov = new OverlayNG(geom0, geom1, opCode);
return(ov.GetResult());
}
