Class BufferSubgraph

java.lang.Object
org.locationtech.jts.operation.buffer.BufferSubgraph
All Implemented Interfaces:
Comparable

class BufferSubgraph extends Object implements Comparable
A connected subset of the graph of DirectedEdges and Nodes. Its edges will generate either
  • a single polygon in the complete buffer, with zero or more holes, or
  • one or more connected holes
Version:
1.7
  • Field Details

  • Constructor Details

    • BufferSubgraph

      public BufferSubgraph()
  • Method Details

    • getDirectedEdges

      public List getDirectedEdges()
    • getNodes

      public List getNodes()
    • getEnvelope

      public Envelope getEnvelope()
      Computes the envelope of the edges in the subgraph. The envelope is cached after being computed.
      Returns:
      the envelope of the graph.
    • getRightmostCoordinate

      public Coordinate getRightmostCoordinate()
      Gets the rightmost coordinate in the edges of the subgraph
    • create

      public void create(Node node)
      Creates the subgraph consisting of all edges reachable from this node. Finds the edges in the graph and the rightmost coordinate.
      Parameters:
      node - a node to start the graph traversal from
    • addReachable

      private void addReachable(Node startNode)
      Adds all nodes and edges reachable from this node to the subgraph. Uses an explicit stack to avoid a large depth of recursion.
      Parameters:
      node - a node known to be in the subgraph
    • add

      private void add(Node node, Stack nodeStack)
      Adds the argument node and all its out edges to the subgraph
      Parameters:
      node - the node to add
      nodeStack - the current set of nodes being traversed
    • clearVisitedEdges

      private void clearVisitedEdges()
    • computeDepth

      public void computeDepth(int outsideDepth)
    • computeDepths

      private void computeDepths(DirectedEdge startEdge)
      Compute depths for all dirEdges via breadth-first traversal of nodes in graph
      Parameters:
      startEdge - edge to start processing with
    • computeNodeDepth

      private void computeNodeDepth(Node n)
    • copySymDepths

      private void copySymDepths(DirectedEdge de)
    • findResultEdges

      public void findResultEdges()
      Find all edges whose depths indicates that they are in the result area(s). Since we want polygon shells to be oriented CW, choose dirEdges with the interior of the result on the RHS. Mark them as being in the result. Interior Area edges are the result of dimensional collapses. They do not form part of the result area boundary.
    • compareTo

      public int compareTo(Object o)
      BufferSubgraphs are compared on the x-value of their rightmost Coordinate. This defines a partial ordering on the graphs such that:

      g1 >= g2 invalid input: '<'==> Ring(g2) does not contain Ring(g1)

      where Polygon(g) is the buffer polygon that is built from g.

      This relationship is used to sort the BufferSubgraphs so that shells are guaranteed to be built before holes.

      Specified by:
      compareTo in interface Comparable