ShapeReader.java

/*
* The JTS Topology Suite is a collection of Java classes that
* implement the fundamental operations required to validate a given
* geo-spatial data set to a known topological specification.
*
* Copyright (C) 2001 Vivid Solutions
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*
* For more information, contact:
*
*     Vivid Solutions
*     Suite #1A
*     2328 Government Street
*     Victoria BC  V8T 5G5
*     Canada
*
*     (250)385-6040
*     www.vividsolutions.com
*/

package com.vividsolutions.jts.awt;

import java.awt.Shape;
import java.awt.geom.AffineTransform;
import java.awt.geom.PathIterator;
import java.util.ArrayList;
import java.util.List;

import com.vividsolutions.jts.algorithm.*;
import com.vividsolutions.jts.geom.*;

/**
 * Converts a Java2D {@link Shape} 
 * or the more general {@link PathIterator} into a {@link Geometry}.
 * <p>
 * The coordinate system for Java2D is typically screen coordinates, 
 * which has the Y axis inverted
 * relative to the usual JTS coordinate system.
 * This is rectified during conversion. 
 * <p>
 * PathIterators to be converted are expected to be linear or flat.
 * That is, they should contain only <tt>SEG_MOVETO</tt>, <tt>SEG_LINETO</tt>, and <tt>SEG_CLOSE</tt> segment types.
 * Any other segment types will cause an exception.
 * 
 * @author Martin Davis
 *
 */
public class ShapeReader 
{
  private static AffineTransform INVERT_Y = AffineTransform.getScaleInstance(1, -1);

  /**
   * Converts a flat path to a {@link Geometry}.
   * 
   * @param pathIt the path to convert
   * @param geomFact the GeometryFactory to use
   * @return a Geometry representing the path
   */
  public static Geometry read(PathIterator pathIt, GeometryFactory geomFact)
  {
    ShapeReader pc = new ShapeReader(geomFact);
    return pc.read(pathIt);
  }
  
  /**
   * Converts a Shape to a Geometry, flattening it first.
   * 
   * @param shp the Java2D shape
   * @param flatness the flatness parameter to use
   * @param geomFact the GeometryFactory to use
   * @return a Geometry representing the shape
   */
  public static Geometry read(Shape shp, double flatness, GeometryFactory geomFact)
  {
    PathIterator pathIt = shp.getPathIterator(INVERT_Y, flatness);
    return ShapeReader.read(pathIt, geomFact);
  }

  private GeometryFactory geometryFactory;
  
  public ShapeReader(GeometryFactory geometryFactory) {
    this.geometryFactory = geometryFactory;
  }

  /**
   * Converts a flat path to a {@link Geometry}.
   * 
   * @param pathIt the path to convert
   * @return a Geometry representing the path
   */
  public Geometry read(PathIterator pathIt)
  {
    List pathPtSeq = toCoordinates(pathIt);
    
    List polys = new ArrayList();
    int seqIndex = 0;
    while (seqIndex < pathPtSeq.size()) {
      // assume next seq is shell 
      // TODO: test this
      Coordinate[] pts = (Coordinate[]) pathPtSeq.get(seqIndex);
      LinearRing shell = geometryFactory.createLinearRing(pts);
      seqIndex++;
      
      List holes = new ArrayList();
      // add holes as long as rings are CCW
      while (seqIndex < pathPtSeq.size() && isHole((Coordinate[]) pathPtSeq.get(seqIndex))) {
        Coordinate[] holePts = (Coordinate[]) pathPtSeq.get(seqIndex);
        LinearRing hole = geometryFactory.createLinearRing(holePts);
        holes.add(hole);
        seqIndex++;
      }
      LinearRing[] holeArray = GeometryFactory.toLinearRingArray(holes);
      polys.add(geometryFactory.createPolygon(shell, holeArray));
    }
    return geometryFactory.buildGeometry(polys);
  }
  
  private boolean isHole(Coordinate[] pts)
  {
    return CGAlgorithms.isCCW(pts);
  }
  
  /**
   * Extracts the points of the paths in a flat {@link PathIterator} into
   * a list of Coordinate arrays.
   * 
   * @param pathIt a path iterator
   * @return a List of Coordinate arrays
   * @throws IllegalArgumentException if a non-linear segment type is encountered
   */
  public static List toCoordinates(PathIterator pathIt)
  {
    List coordArrays = new ArrayList();
    while (! pathIt.isDone()) {
      Coordinate[] pts = nextCoordinateArray(pathIt);
      if (pts == null)
        break;
      coordArrays.add(pts);
    }
    return coordArrays;
  }
  
  private static Coordinate[] nextCoordinateArray(PathIterator pathIt)
  {
    double[] pathPt = new double[6];
    CoordinateList coordList = null;
    boolean isDone = false;
    while (! pathIt.isDone()) {
      int segType = pathIt.currentSegment(pathPt);
      switch (segType) {
      case PathIterator.SEG_MOVETO:
        if (coordList != null) {
          // don't advance pathIt, to retain start of next path if any
          isDone = true;
        }
        else {
          coordList = new CoordinateList();
          coordList.add(new Coordinate(pathPt[0], pathPt[1]));
          pathIt.next();
        }
        break;
      case PathIterator.SEG_LINETO:
        coordList.add(new Coordinate(pathPt[0], pathPt[1]));
        pathIt.next();
        break;
      case PathIterator.SEG_CLOSE:  
        coordList.closeRing();
        pathIt.next();
        isDone = true;   
        break;
      default:
      	throw new IllegalArgumentException("unhandled (non-linear) segment type encountered");
      }
      if (isDone) 
        break;
    }
    return coordList.toCoordinateArray();
  }

}