libjava/classpath/gnu/java/awt/java2d/PolyEdge.java

   1 /* PolyEdge.java -- An edge in a polygon, used for polygon filling
   2    Copyright (C) 2006 Free Software Foundation, Inc.
   3
   4 This file is part of GNU Classpath.
   5
   6 GNU Classpath is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 2, or (at your option)
   9 any later version.
  10
  11 GNU Classpath is distributed in the hope that it will be useful, but
  12 WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14 General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GNU Classpath; see the file COPYING.  If not, write to the
  18 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  19 02110-1301 USA.
  20
  21 Linking this library statically or dynamically with other modules is
  22 making a combined work based on this library.  Thus, the terms and
  23 conditions of the GNU General Public License cover the whole
  24 combination.
  25
  26 As a special exception, the copyright holders of this library give you
  27 permission to link this library with independent modules to produce an
  28 executable, regardless of the license terms of these independent
  29 modules, and to copy and distribute the resulting executable under
  30 terms of your choice, provided that you also meet, for each linked
  31 independent module, the terms and conditions of the license of that
  32 module.  An independent module is a module which is not derived from
  33 or based on this library.  If you modify this library, you may extend
  34 this exception to your version of the library, but you are not
  35 obligated to do so.  If you do not wish to do so, delete this
  36 exception statement from your version. */
  37
  38
  39 package gnu.java.awt.java2d;
  40
  41 /**
  42  * An edge in a polygon. This is used by the scanline conversion algorithm
  43  * implemented in {@link AbstractGraphics2D#rawFillShape}.
  44  *
  45  * @author Roman Kennke (kennke@aicas.com)
  46  */
  47 public class PolyEdge
  48   implements Comparable
  49 {
  50
  51   /**
  52    * The start and end coordinates of the edge. y0 is always smaller or equal
  53    * than y1.
  54    */
  55   public double x0, y0, x1, y1;
  56
  57   /**
  58    * The slope of the edge. This is dx / dy.
  59    */
  60   double slope;
  61
  62   /**
  63    * The intersection of this edge with the current scanline.
  64    */
  65   double xIntersection;
  66
  67   /**
  68    * Creates a new PolyEdge with the specified coordinates.
  69    *
  70    * @param x0 the starting point, x coordinate
  71    * @param y0 the starting point, y coordinate
  72    * @param x1 the end point, x coordinate
  73    * @param y1 the end point, y coordinate
  74    */
  75   PolyEdge(double x0, double y0, double x1, double y1)
  76   {
  77     if (y0 < y1)
  78       {
  79         this.x0 = x0;
  80         this.y0 = y0;
  81         this.x1 = x1;
  82         this.y1 = y1;
  83       }
  84     else
  85       {
  86         this.x0 = x1;
  87         this.y0 = y1;
  88         this.x1 = x0;
  89         this.y1 = y0;
  90       }
  91     slope = (this.x1 - this.x0) / (this.y1 - this.y0);
  92     if (this.y0 == this.y1) // Horizontal edge.
  93       xIntersection = Math.min(this.x0, this.x1);
  94     else
  95       xIntersection = this.x0 + slope * (Math.ceil(this.y0) - this.y0);
  96   }
  97
  98   /**
  99    * Sorts PolyEdges by the x coordinate from the minimum x value.
 100    */
 101   public int compareTo(Object o)
 102   {
 103     PolyEdge other = (PolyEdge) o;
 104     int comp = 0;
 105     if (x0 < other.x0)
 106       comp = -1;
 107     else if (x0 > other.x0)
 108       comp = 1;
 109     return comp;
 110   }
 111
 112   public String toString()
 113   {
 114     return "Edge: " + x0 + ", " + y0 + ", " + x1 + ", " + y1 + ", slope: "
 115            + slope + ", xIntersection: " + xIntersection;
 116   }
 117 }