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 }