gov/nasa/worldwind/geom/SurfacePolygon.java

   1 /*
   2 Copyright (C) 2001, 2006 United States Government
   3 as represented by the Administrator of the
   4 National Aeronautics and Space Administration.
   5 All Rights Reserved.
   6 */
   7 package gov.nasa.worldwind.geom;
   8
   9 import java.awt.*;
  10 import java.awt.geom.*;
  11 import java.awt.image.*;
  12 import java.util.*;
  13
  14 /**
  15  * @author tag
  16  * @version $Id: SurfacePolygon.java 2133 2007-06-23 02:08:28Z patrickmurris $
  17  */
  18 public class SurfacePolygon extends SurfaceShape
  19 {
  20
  21     /**
  22      * A Renderable polygon shape defined by a list of LatLon
  23      *
  24      * @param positions   the list of LatLon positions that makes the polygon
  25      * @param color       the interior fill color
  26      * @param borderColor the border color
  27      */
  28     public SurfacePolygon(Iterable<LatLon> positions, Color color, Color borderColor)
  29     {
  30         super(positions, color, borderColor);
  31     }
  32
  33     /**
  34      * A Renderable polygon shape defined by a list of LatLon
  35      *
  36      * @param positions the list of LatLon positions that makes the polygon
  37      */
  38     public SurfacePolygon(Iterable<LatLon> positions)
  39     {
  40         super(positions, null, null);
  41     }
  42
  43     /**
  44      * Draw all or part of the shape that intersects a given Sector into the given BufferedImage
  45      */
  46     protected final BufferedImage drawShape(BufferedImage image, Sector sector)
  47     {
  48         double minLat = sector.getMinLatitude().getDegrees();
  49         double minLon = sector.getMinLongitude().getDegrees();
  50         double dLat = sector.getDeltaLatDegrees();
  51         double dLon = sector.getDeltaLonDegrees();
  52
  53         // Note : WWJ-36 negate latScale to define path upside-down
  54         // (will be drawn with a mirror transform - this gets paint patterns right)
  55         double latScale = dLat > 0 ? -image.getHeight() / dLat : 0;
  56         double lonScale = dLon > 0 ? image.getWidth() / dLon : 0;
  57
  58         // If we may cross +-180 degrees longitude, then offset
  59         // all longitudes 180 degrees the other way
  60         double lonOffset = 0;
  61         if (sector.getMaxLongitude().getDegrees() == 180 && dLon < 180)
  62             lonOffset = -180;
  63         if (sector.getMinLongitude().getDegrees() == -180 && dLon < 180)
  64             lonOffset = 180;
  65
  66         GeneralPath path = new GeneralPath();
  67
  68         Iterator<LatLon> positions = this.getPositions().iterator();
  69         if (!positions.hasNext())
  70             return image;
  71
  72         // Start position
  73         LatLon pos = this.computeDrawLatLon(positions.next(), sector, lonOffset);
  74         path.moveTo(
  75             (float) (lonScale * (pos.getLongitude().getDegrees() - minLon - lonOffset)),
  76             (float) (latScale * (pos.getLatitude().getDegrees() - minLat)));
  77
  78         while (positions.hasNext())
  79         {
  80             // Next position
  81             LatLon posNext = this.computeDrawLatLon(positions.next(), sector, lonOffset);
  82             // Compute number of necessary steps
  83             int numIntervals = (int) Math.max(1d,
  84                 this.getNumEdgeIntervalsPerDegree() *
  85                     LatLon.sphericalDistance(pos, posNext).degrees);
  86             double delta = 1d / numIntervals;
  87             // Draw segments to next position
  88             for (int i = 1; i < numIntervals; i++)
  89             {
  90                 // In between steps
  91                 LatLon p = LatLon.interpolate(i * delta, pos, posNext);
  92                 path.lineTo(
  93                     (float) (lonScale * (p.getLongitude().getDegrees() - minLon - lonOffset)),
  94                     (float) (latScale * (p.getLatitude().getDegrees() - minLat)));
  95             }
  96
  97             // Set the last point directly to avoid any round-off error in the iteration above.
  98             path.lineTo(
  99                 (float) (lonScale * (posNext.getLongitude().getDegrees() - minLon - lonOffset)),
 100                 (float) (latScale * (posNext.getLatitude().getDegrees() - minLat)));
 101             // Next
 102
 103             pos = posNext;
 104         }
 105
 106         Graphics2D g2 = image.createGraphics();
 107         // Set mirror Y transform
 108         g2.setTransform(AffineTransform.getScaleInstance(1, -1));
 109         // Set antiliasing hint
 110         if (this.isAntiAlias())
 111             g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
 112         // Draw interior
 113         if (this.isDrawInterior())
 114         {
 115             g2.setPaint(this.getPaint());
 116             g2.fill(path);
 117         }
 118         // Draw border
 119         if (this.isDrawBorder())
 120         {
 121             g2.setPaint(this.getBorderColor());
 122             g2.setStroke(this.getStroke());
 123             g2.draw(path);
 124         }
 125
 126         return image;
 127     }
 128
 129     /**
 130      * Returns the drawing LatLon relative to a given Sector and a longitude offset Can go beyond +-180 degrees
 131      * longitude if the offset is zero
 132      * @param pos the real LatLon
 133      * @param sector the drawing Sector
 134      * @param lonOffset the current longitude offset in degrees
 135      * @return the appropiate drawing LatLon
 136      */
 137     private LatLon computeDrawLatLon(LatLon pos, Sector sector, double lonOffset)
 138     {
 139         int directionOffset;
 140         directionOffset = sector.getMaxLongitude().degrees - pos.getLongitude().getDegrees() > 180 ?
 141             360 : 0;
 142         directionOffset = pos.getLongitude().getDegrees() - sector.getMinLongitude().getDegrees() > 180 ?
 143             -360 : directionOffset;
 144         return LatLon.fromDegrees(pos.getLatitude().getDegrees(),
 145             pos.getLongitude().getDegrees() + directionOffset + lonOffset);
 146     }
 147 }