/// <summary>
/// Calculates the overlap between the source and the target. If the target is disjoint or within
/// the source, an empty list is returned.
/// </summary>
/// <returns></returns>
public IList <Linestring> IntersectXY()
{
Assert.True(_sourceRing.ClockwiseOriented == true,
"The source is not oriented clockwise or it is vertical.");
Assert.True(_target.IsClosed, "The target is not a closed linestring.");
Assert.NotNull(_target.ClockwiseOriented, "The target is vertical");
if (SourceEqualsTargetXY())
{
// Target equals source in XY - return source if both are positive:
Linestring resultRing =
IsExterior(_sourceRing) && IsExterior(_target)
? _sourceRing.Clone()
: Linestring.CreateEmpty();
return(new List <Linestring> {
resultRing
});
}
return(_target.ClockwiseOriented.Value
? GetRightSideRings()
: GetLeftSideRings());
}
/// <summary>
/// Removes the overlap between the source and the target from the source.
/// - Vertical targets are not supported.
/// - Counter-clockwise oriented (interior) rings are supported. The counter-clockwise
/// rings have their 'interior' on the outside, i.e. their overlap 'removed' on the
/// outside, if the target is also counter-clockwise (i.e. inner rings are unioned).
/// - If the target is equal to the source in XY, the result is one empty Linestring.
/// - If the target is disjoint or completely within the source, an empty list is returned.
/// </summary>
/// <returns></returns>
public IList <Linestring> RemoveOverlapXY()
{
Assert.True(_target.IsClosed, "The target is not a closed linestring.");
Assert.NotNull(_target.ClockwiseOriented, "The target is vertical");
if (SourceEqualsTargetXY())
{
// Target equals source in XY - positive rings cancel each other out:
Linestring resultRing =
IsExterior(_sourceRing) && IsExterior(_target)
? Linestring.CreateEmpty()
: _sourceRing.Clone();
return(new List <Linestring> {
resultRing
});
}
return(_target.ClockwiseOriented.Value
? GetLeftSideRings()
: GetRightSideRings());
}