git.gag.com Git - sw/motorsim/blob - src/com/billkuker/rocketry/motorsim/grain/ShapeUtil.java

   1 package com.billkuker.rocketry.motorsim.grain;\r
   2 import java.awt.geom.AffineTransform;\r
   3 import java.awt.geom.GeneralPath;\r
   4 import java.awt.geom.PathIterator;\r
   5 import java.util.HashSet;\r
   6 import java.util.Set;\r
   7 \r
   8 import javax.measure.quantity.Area;\r
   9 import javax.measure.quantity.Length;\r
  10 import javax.measure.unit.SI;\r
  11 \r
  12 import org.jscience.physics.amount.Amount;\r
  13 public class ShapeUtil {\r
  14         private ShapeUtil(){}\r
  15 \r
  16         /*\r
  17          * Return the Area of a singular polygon (NO HOLES OR DISJOINT PARTS).\r
  18          * Coordinates assumed to be in MM.\r
  19          * http://valis.cs.uiuc.edu/~sariel/research/CG/compgeom/msg00831.html\r
  20          * http://stackoverflow.com/questions/451426/how-do-i-calculate-the-surface-area-of-a-2d-polygon\r
  21          * http://www.wikihow.com/Calculate-the-Area-of-a-Polygon\r
  22          * According to http://www.geog.ubc.ca/courses/klink/gis.notes/ncgia/u33.html\r
  23          * this algorithm works OK with holes, and it seems to (see test)\r
  24          */\r
  25         public static Amount<Area> area(java.awt.geom.Area a) {\r
  26                 //if ( !a.isSingular() )\r
  27                         //throw new IllegalArgumentException("Can not calculate area of non-singular shape!");\r
  28                 PathIterator i = a.getPathIterator(new AffineTransform(), .001);\r
  29                 \r
  30                 \r
  31                 double x = 0, y = 0, sx = 0, sy = 0;\r
  32                 double nx, ny;\r
  33                 double area = 0;\r
  34                 while (!i.isDone()) {\r
  35                         double coords[] = new double[6];\r
  36                         int type = i.currentSegment(coords);\r
  37                         switch( type ){\r
  38                         case PathIterator.SEG_CLOSE:\r
  39                                 //Go back to the start\r
  40                                 nx = sx;\r
  41                                 ny = sy;\r
  42                                 area += x * ny;\r
  43                                 area -= y * nx;\r
  44                                 break;\r
  45                         case PathIterator.SEG_LINETO:\r
  46                                 nx = coords[0];\r
  47                                 ny = coords[1];\r
  48                                 area += x * ny;\r
  49                                 area -= y * nx;\r
  50         \r
  51                                 //Remember the last points\r
  52                                 x = nx;\r
  53                                 y = ny;\r
  54                                 \r
  55                                 break;\r
  56                         case PathIterator.SEG_MOVETO:\r
  57                                 //Remember the starting point\r
  58                                 x = sx = coords[0];\r
  59                                 y = sy = coords[1];\r
  60                                 break;\r
  61                         default:\r
  62                                 throw new Error("Bad segment type from Flattening Path Iterator");\r
  63                         }\r
  64                         i.next();\r
  65                 }\r
  66                 \r
  67                 area = area / 2.0; // Result so far is double the signed area\r
  68                 \r
  69                 if ( area < 0 ){ //Depending on winding it could be negative\r
  70                         area = area * -1.0;\r
  71                 }\r
  72                 \r
  73                 \r
  74                 return Amount.valueOf(area, SI.MILLIMETER.pow(2)).to(Area.UNIT);\r
  75         }\r
  76 \r
  77         public static Amount<Length> perimeter(java.awt.geom.Area a) {\r
  78                 //TODO: I think I need to handle seg_close!!\r
  79                 PathIterator i = a.getPathIterator(new AffineTransform(), .001);\r
  80                 double x = 0, y = 0;\r
  81                 double len = 0;\r
  82                 while (!i.isDone()) {\r
  83                         double coords[] = new double[6];\r
  84                         int type = i.currentSegment(coords);\r
  85                         if (type == PathIterator.SEG_LINETO) {\r
  86                                 // System.out.println("Line");\r
  87                                 double nx = coords[0];\r
  88                                 double ny = coords[1];\r
  89                                 // System.out.println(x+","+y+ " to " + nx+"," + ny);\r
  90                                 len += Math.sqrt(Math.pow(x - nx, 2) + Math.pow(y - ny, 2));\r
  91                                 x = nx;\r
  92                                 y = ny;\r
  93                         } else if (type == PathIterator.SEG_MOVETO) {\r
  94                                 // System.out.println("Move");\r
  95                                 x = coords[0];\r
  96                                 y = coords[1];\r
  97                         } else {\r
  98                                 // System.err.println("Got " + type);\r
  99                         }\r
 100                         i.next();\r
 101                 }\r
 102                 return Amount.valueOf(len, SI.MILLIMETER);\r
 103         }\r
 104 \r
 105         /*\r
 106          * Separate an area into multiple distinct area.\r
 107          * Area CAN NOT HAVE HOLES. HOLES WILL BE RETURNED AS AREAS,\r
 108          * SO A DONUT WILL TURN INTO TWO CIRCLES.\r
 109          */\r
 110         public static Set<java.awt.geom.Area> separate(java.awt.geom.Area a) {\r
 111                 Set<java.awt.geom.Area> res = new HashSet<java.awt.geom.Area>();\r
 112                 PathIterator i = a.getPathIterator(new AffineTransform());\r
 113                 GeneralPath cur = null;\r
 114         \r
 115                 while (!i.isDone()) {\r
 116                         double coords[] = new double[6];\r
 117                         int type = i.currentSegment(coords);\r
 118                         switch (type) {\r
 119                         case PathIterator.SEG_CLOSE:\r
 120                                 cur.closePath();\r
 121                                 if (cur != null ){\r
 122                                         java.awt.geom.Area area = new java.awt.geom.Area(cur);\r
 123                                         if ( !a.isEmpty() )\r
 124                                                 res.add(area);\r
 125                                 }\r
 126                                 cur = new GeneralPath(i.getWindingRule());\r
 127                                 break;\r
 128                         case PathIterator.SEG_MOVETO:\r
 129                                 if (cur != null ){\r
 130                                         java.awt.geom.Area area = new java.awt.geom.Area(cur);\r
 131                                         if ( !a.isEmpty() )\r
 132                                                 res.add(area);\r
 133                                 }\r
 134                                 cur = new GeneralPath(i.getWindingRule());\r
 135                                 cur.moveTo(coords[0], coords[1]);\r
 136                                 break;\r
 137                         case PathIterator.SEG_CUBICTO:\r
 138                                 cur.curveTo(coords[0], coords[1], coords[2], coords[3],\r
 139                                                 coords[4], coords[5]);\r
 140                                 break;\r
 141                         case PathIterator.SEG_LINETO:\r
 142                                 cur.lineTo(coords[0], coords[1]);\r
 143                                 break;\r
 144                         case PathIterator.SEG_QUADTO:\r
 145                                 cur.quadTo(coords[0], coords[1], coords[2], coords[3]);\r
 146                                 break;\r
 147         \r
 148                         }\r
 149                         i.next();\r
 150                 }\r
 151         \r
 152                 return res;\r
 153         }\r
 154         \r
 155         \r
 156 }\r