Class MaximumInscribedCircle
java.lang.Object
org.locationtech.jts.algorithm.construct.MaximumInscribedCircle
Constructs the Maximum Inscribed Circle for a
polygonal
Geometry
, up to a specified tolerance.
The Maximum Inscribed Circle is determined by a point in the interior of the area
which has the farthest distance from the area boundary,
along with a boundary point at that distance.
In the context of geography the center of the Maximum Inscribed Circle is known as the Pole of Inaccessibility. A cartographic use case is to determine a suitable point to place a map label within a polygon.
The radius length of the Maximum Inscribed Circle is a measure of how "narrow" a polygon is. It is the distance at which the negative buffer becomes empty.
The class supports polygons with holes and multipolygons.
The implementation uses a successive-approximation technique over a grid of square cells covering the area geometry. The grid is refined using a branch-and-bound algorithm. Point containment and distance are computed in a performant way by using spatial indexes.
Future Enhancements
- Support a polygonal constraint on placement of center
- Author:
- Martin Davis
- See Also:
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Constructor Summary
ConstructorsConstructorDescriptionMaximumInscribedCircle
(Geometry polygonal, double tolerance) Creates a new instance of a Maximum Inscribed Circle computation. -
Method Summary
Modifier and TypeMethodDescriptionGets the center point of the maximum inscribed circle (up to the tolerance distance).static Point
Computes the center point of the Maximum Inscribed Circle of a polygonal geometry, up to a given tolerance distance.Gets a line representing a radius of the Largest Empty Circle.static LineString
getRadiusLine
(Geometry polygonal, double tolerance) Computes a radius line of the Maximum Inscribed Circle of a polygonal geometry, up to a given tolerance distance.Gets a point defining the radius of the Maximum Inscribed Circle.
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Constructor Details
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MaximumInscribedCircle
Creates a new instance of a Maximum Inscribed Circle computation.- Parameters:
polygonal
- an areal geometrytolerance
- the distance tolerance for computing the centre point (must be positive)- Throws:
IllegalArgumentException
- if the tolerance is non-positive, or the input geometry is non-polygonal or empty.
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Method Details
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getCenter
Computes the center point of the Maximum Inscribed Circle of a polygonal geometry, up to a given tolerance distance.- Parameters:
polygonal
- a polygonal geometrytolerance
- the distance tolerance for computing the center point- Returns:
- the center point of the maximum inscribed circle
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getRadiusLine
Computes a radius line of the Maximum Inscribed Circle of a polygonal geometry, up to a given tolerance distance.- Parameters:
polygonal
- a polygonal geometrytolerance
- the distance tolerance for computing the center point- Returns:
- a line from the center to a point on the circle
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getCenter
Gets the center point of the maximum inscribed circle (up to the tolerance distance).- Returns:
- the center point of the maximum inscribed circle
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getRadiusPoint
Gets a point defining the radius of the Maximum Inscribed Circle. This is a point on the boundary which is nearest to the computed center of the Maximum Inscribed Circle. The line segment from the center to this point is a radius of the constructed circle, and this point lies on the boundary of the circle.- Returns:
- a point defining the radius of the Maximum Inscribed Circle
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getRadiusLine
Gets a line representing a radius of the Largest Empty Circle.- Returns:
- a line from the center of the circle to a point on the edge
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