[RGEOS]绘制多边形Polygon

 绘制OGIS定义的Polygon

 1    public void DrawPolygon(Polygon pol, Brush brush, Pen pen, bool clip)

 2         {

 3             gc = Graphics.FromHwnd(Handle);

 4             if (pol.ExteriorRing == null)

 5                 return;

 6             if (pol.ExteriorRing.Vertices.Count > 2)

 7             {

 8                 //Use a graphics path instead of DrawPolygon. DrawPolygon has a problem with several interior holes

 9                 GraphicsPath gp = new GraphicsPath();

10 

11                 //Add the exterior polygon

12                 PointF[] pts = TransformLineString(pol.ExteriorRing);

13                 if (!clip)

14                     gp.AddPolygon(LimitValues(pts, extremeValueLimit));

15                 else

16                     DrawPolygonClipped(gp, pts, (int)100, (int)100);

17 

18                 //Add the interior polygons (holes)

19 

20                 for (int i = 0; i < pol.InteriorRings.Count; i++)

21                 {

22                     PointF[] pts1 = TransformLineString(pol.InteriorRings[i]);

23                     if (!clip)

24                         gp.AddPolygon(LimitValues(pts1, extremeValueLimit));

25                     else

26                         DrawPolygonClipped(gp, pts1, (int)100, (int)100);

27                 }

28 

29                 // Only render inside of polygon if the brush isn't null or isn't transparent

30                 if (brush != null && brush != Brushes.Transparent)

31                     gc.FillPath(brush, gp);

32                 // Create an outline if a pen style is available

33                 if (pen != null)

34                     gc.DrawPath(pen, gp);

35                 gc.Dispose();

36             }

37         }

 

1   public static PointF[] TransformLineString(LineString line)

2         {

3             PointF[] v = new PointF[line.Vertices.Count];

4             for (int i = 0; i < line.Vertices.Count; i++)

5                 v[i] = new PointF((float)line.Vertices[i].X, (float)line.Vertices[i].Y);

6             return v;

7         }

 

  1         internal static PointF[] clipPolygon(PointF[] vertices, int width, int height)

  2         {

  3             float deltax, deltay, xin, xout, yin, yout;

  4             float tinx, tiny, toutx, touty, tin1, tin2, tout;

  5             float x1, y1, x2, y2;

  6 

  7             List<PointF> line = new List<PointF>();

  8             if (vertices.Length <= 1) /* nothing to clip */

  9                 return vertices;

 10 

 11             for (int i = 0; i < vertices.Length - 1; i++)

 12             {

 13                 x1 = vertices[i].X;

 14                 y1 = vertices[i].Y;

 15                 x2 = vertices[i + 1].X;

 16                 y2 = vertices[i + 1].Y;

 17 

 18                 deltax = x2 - x1;

 19                 if (deltax == 0)

 20                 {

 21                     // bump off of the vertical

 22                     deltax = (x1 > 0) ? -nearZero : nearZero;

 23                 }

 24                 deltay = y2 - y1;

 25                 if (deltay == 0)

 26                 {

 27                     // bump off of the horizontal

 28                     deltay = (y1 > 0) ? -nearZero : nearZero;

 29                 }

 30 

 31                 if (deltax > 0)

 32                 {

 33                     //  points to right

 34                     xin = 0;

 35                     xout = width;

 36                 }

 37                 else

 38                 {

 39                     xin = width;

 40                     xout = 0;

 41                 }

 42 

 43                 if (deltay > 0)

 44                 {

 45                     //  points up

 46                     yin = 0;

 47                     yout = height;

 48                 }

 49                 else

 50                 {

 51                     yin = height;

 52                     yout = 0;

 53                 }

 54 

 55                 tinx = (xin - x1) / deltax;

 56                 tiny = (yin - y1) / deltay;

 57 

 58                 if (tinx < tiny)

 59                 {

 60                     // hits x first

 61                     tin1 = tinx;

 62                     tin2 = tiny;

 63                 }

 64                 else

 65                 {

 66                     // hits y first

 67                     tin1 = tiny;

 68                     tin2 = tinx;

 69                 }

 70 

 71                 if (1 >= tin1)

 72                 {

 73                     if (0 < tin1)

 74                         line.Add(new PointF(xin, yin));

 75 

 76                     if (1 >= tin2)

 77                     {

 78                         toutx = (xout - x1) / deltax;

 79                         touty = (yout - y1) / deltay;

 80 

 81                         tout = (toutx < touty) ? toutx : touty;

 82 

 83                         if (0 < tin2 || 0 < tout)

 84                         {

 85                             if (tin2 <= tout)

 86                             {

 87                                 if (0 < tin2)

 88                                 {

 89                                     if (tinx > tiny)

 90                                         line.Add(new PointF(xin, y1 + tinx * deltay));

 91                                     else

 92                                         line.Add(new PointF(x1 + tiny * deltax, yin));

 93                                 }

 94 

 95                                 if (1 > tout)

 96                                 {

 97                                     if (toutx < touty)

 98                                         line.Add(new PointF(xout, y1 + toutx * deltay));

 99                                     else

100                                         line.Add(new PointF(x1 + touty * deltax, yout));

101                                 }

102                                 else

103                                     line.Add(new PointF(x2, y2));

104                             }

105                             else

106                             {

107                                 if (tinx > tiny)

108                                     line.Add(new PointF(xin, yout));

109                                 else

110                                     line.Add(new PointF(xout, yin));

111                             }

112                         }

113                     }

114                 }

115             }

116             if (line.Count > 0)

117                 line.Add(new PointF(line[0].X, line[0].Y));

118 

119             return line.ToArray();

120         }

121 

122         private void DrawPolygonClipped(GraphicsPath gp, PointF[] polygon, int width, int height)

123         {

124             ClipState clipState = DetermineClipState(polygon, width, height);

125             if (clipState == ClipState.Within)

126             {

127                 gp.AddPolygon(polygon);

128             }

129             else if (clipState == ClipState.Intersecting)

130             {

131                 PointF[] clippedPolygon = clipPolygon(polygon, width, height);

132                 if (clippedPolygon.Length > 2)

133                     gp.AddPolygon(clippedPolygon);

134             }

135         }