MedialAxis

java.lang.Object
- org.gvsig.fmap.geom.jts.util.MedialAxis

```
public class MedialAxis
extends java.lang.Object
```
Based on ideas from https://www.cs.ubc.ca/labs/imager/th/2003/Tam2004/Tam2004.pdf and Voronoi Ball/Disk Models for Computational Shape Applications
Produces a directed acyclic graph of the MD / more specifically rooted tree
Medial Axis library models medial axes of shapes as a (rooted) tree of medial disks. Medial disks reference a parent and have upto 3 children (the medial axis bifurcates/forks at disks with 2 children). The root is the disk with the largest circumcirle, also the single disk that trifurcates. All disks have an indegree of 1.
For geometries of genus zero, the graph is naturally a tree. For objects with holes, we break each cycle by imposing an appropriate breakpoint in the loop. This is only for the purposes of traversing the graph without running into infinite loops. In order to preserve the topology of the original object, cycles are never pruned
Decompose the disk coordinates into curves.
If angle of successive line branches is the same, merge them
* One way to get a smoother initial axis (i.e. without pruning) is to apply on a smoothed version of the shape.

Nested Class Summary

Nested Classes
Modifier and Type	Class and Description
`class`	`MedialAxis.Branch` Branches are series of successive disks found in between.
`class`	`MedialAxis.Edge` Edges are straight-line segments that connect two adjacent disks.
`class`	`MedialAxis.MedialDisk` Voronoi Disk. medial disk?

Field Summary

Fields
Modifier and Type Field and Description

boolean debug

MedialAxis.MedialDisk furthestNode

MedialAxis.MedialDisk rootNode

Fields
Modifier and Type	Field and Description
`boolean`	`debug`
`MedialAxis.MedialDisk`	`furthestNode`
`MedialAxis.MedialDisk`	`rootNode`

Constructor Summary

Constructors
Constructor and Description

MedialAxis(Coordinate[] coordinates)

MedialAxis(Geometry g)
The medial axis is computed for the geometry during construction.

Constructors
Constructor and Description
`MedialAxis(Coordinate[] coordinates)`
`MedialAxis(Geometry g)` The medial axis is computed for the geometry during construction.

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`void`	`calcFeatureArea()`
`java.util.List<MedialAxis.MedialDisk>`	`getAncestors(MedialAxis.MedialDisk child)` The ancestors of a node d are the nodes on the path from d to the root.
`java.util.List<MedialAxis.MedialDisk>`	`getBifurcations()` Nodes/medial disks with two descendent lineages (two children disks).
`java.util.List<MedialAxis.Branch>`	`getBranches()` Aka features, aka branches Segment is a linear portion of medial disks.
`java.util.List<MedialAxis.MedialDisk>`	`getDescendants(MedialAxis.MedialDisk parent)` Returns the children of a disk into a linear array
`java.util.List<MedialAxis.MedialDisk>`	`getDescendants(MedialAxis.MedialDisk parent, int maxDepth)`
`java.util.List<MedialAxis.MedialDisk>`	`getDisks()`
`Geometry`	`getDissolvedGeometry()` Returns a JTS geometry where medial axis edges are dissolved into a set of maximal-length Linestrings.
`java.util.Collection<MedialAxis.Edge>`	`getEdges()`
`java.util.List<MedialAxis.MedialDisk>`	`getLeaves()` End nodes / A VDs of degree 1/no children
`LineMergeGraph`	`getLineMergeGraph()` Get the medial axis in the form of an undirected planar graph.
`java.util.List<MedialAxis.Edge>`	`getPrunedEdges(double threshold)` Returns a subset of the axis' edges; in this method edges are pruned by their axial gradient value.
`java.util.List<MedialAxis.Edge>`	`getPrunedEdges(double axialThreshold, double distanceThreshold)` Returns a subset of the axis' edges; in this method edges are pruned by their axial gradient value and axis distance from the root node.
`java.util.List<MedialAxis.Edge>`	`getPrunedEdges(double axialThreshold, double distanceThreshold, double areaThreshold)`
`static void`	`main(java.lang.String[] args)`
`MedialAxis.MedialDisk`	`nearestDisk(Coordinate coordinate)`
`MedialAxis.MedialDisk`	`nearestDisk(double x, double y)`

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - rootNode
```
public MedialAxis.MedialDisk rootNode
```
  - furthestNode
```
public MedialAxis.MedialDisk furthestNode
```
  - debug
```
public boolean debug
```
- Constructor Detail
  - MedialAxis
```
public MedialAxis(Coordinate[] coordinates)
```
  - MedialAxis
```
public MedialAxis(Geometry g)
```
    The medial axis is computed for the geometry during construction.
    
    Parameters:
    
    g - Geometry whose medial axis to compute. Can contain holes. Must not be a multigeometry
- Method Detail
  - getDisks
```
public java.util.List<MedialAxis.MedialDisk> getDisks()
```
  - nearestDisk
```
public MedialAxis.MedialDisk nearestDisk(double x,
                                         double y)
```
  - nearestDisk
```
public MedialAxis.MedialDisk nearestDisk(Coordinate coordinate)
```
  - getDescendants
```
public java.util.List<MedialAxis.MedialDisk> getDescendants(MedialAxis.MedialDisk parent)
```
    Returns the children of a disk into a linear array
    
    Parameters:
    
    parent - contains chil out: contains children and the parent (at position 0)
    
    Returns:
  - getDescendants
```
public java.util.List<MedialAxis.MedialDisk> getDescendants(MedialAxis.MedialDisk parent,
                                                            int maxDepth)
```
  - getAncestors
```
public java.util.List<MedialAxis.MedialDisk> getAncestors(MedialAxis.MedialDisk child)
```
    The ancestors of a node d are the nodes on the path from d to the root. This includes node d.
    TODO another method that returns paths from fork VDs in the ancestors (Except rootnode)
    
    Parameters:
    
    child -
    
    Returns:
  - getDissolvedGeometry
```
public Geometry getDissolvedGeometry()
```
    Returns a JTS geometry where medial axis edges are dissolved into a set of maximal-length Linestrings. The output can be further simplfied with DouglasPeuckerSimplifier for example. * Returns a simplified medial axis graph leaving only maximal-length lines in which every unique segment appears once only. The output lines run between node vertices of the input, which are vertices which have either degree 1, or degree 3 or greater.
    
    Returns:
  - getLineMergeGraph
```
public LineMergeGraph getLineMergeGraph()
```
    Get the medial axis in the form of an undirected planar graph. The graph is based on the dissolved geometry.
    
    Returns:
  - getLeaves
```
public java.util.List<MedialAxis.MedialDisk> getLeaves()
```
    End nodes / A VDs of degree 1/no children
    
    Returns:
  - getBifurcations
```
public java.util.List<MedialAxis.MedialDisk> getBifurcations()
```
    Nodes/medial disks with two descendent lineages (two children disks). Note the root node (a trifurcating node) is not included in the output.
    
    Returns:
  - getEdges
```
public java.util.Collection<MedialAxis.Edge> getEdges()
```
    Returns:
    
    list of edges (in breadth-first order from the root node) connecting medial disks.
  - getBranches
```
public java.util.List<MedialAxis.Branch> getBranches()
```
    Aka features, aka branches Segment is a linear portion of medial disks.
    
    Returns:
    
    List of branches
  - getPrunedEdges
```
public java.util.List<MedialAxis.Edge> getPrunedEdges(double threshold)
```
    Returns a subset of the axis' edges; in this method edges are pruned by their axial gradient value. Edges with negative axial gradient values indicate a narrowing of the shape along that edge, and are more likely to be noise. The threshold takes into account this shape's minimum and maximum axial values when filtering.
    Presently this method prunes based on global min and max axial values (rather than per branch).
    
    Parameters:
    
    threshold - between 0...1, where 0 is no pruning and 1 is maximal pruning. the shape may be fully pruned before threshold = 1
    
    Returns:
  - getPrunedEdges
```
public java.util.List<MedialAxis.Edge> getPrunedEdges(double axialThreshold,
                                                      double distanceThreshold)
```
    Returns a subset of the axis' edges; in this method edges are pruned by their axial gradient value and axis distance from the root node.
    
    Parameters:
    
    axialThreshold - between 0...1, where 0 is no pruning and 1 is maximal pruning
    
    distanceThreshold - between 0...1, where 0 is no pruning and 1 is maximal pruning
    
    Returns:
  - getPrunedEdges
```
public java.util.List<MedialAxis.Edge> getPrunedEdges(double axialThreshold,
                                                      double distanceThreshold,
                                                      double areaThreshold)
```
    Parameters:
    
    axialThreshold -
    
    distanceThreshold -
    
    areaThreshold - between 0...1, where 0 is no pruning and 1 is maximal pruning for this feature
    
    Returns:
  - calcFeatureArea
```
public void calcFeatureArea()
```
  - main
```
public static void main(java.lang.String[] args)
                 throws ParseException
```
    Throws:
    
    ParseException

Class MedialAxis

Nested Class Summary

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

rootNode

furthestNode

debug

Constructor Detail

MedialAxis

MedialAxis

Method Detail

getDisks

nearestDisk

nearestDisk

getDescendants

getDescendants

getAncestors

getDissolvedGeometry

getLineMergeGraph

getLeaves

getBifurcations

getEdges

getBranches

getPrunedEdges

getPrunedEdges

getPrunedEdges

calcFeatureArea

main