[SharpMap] 屏幕坐标和Map坐标转换

1. SharpMap中屏幕坐标和地图Map坐标转换：

 1 using System.Drawing;
 2 using GeoAPI.Geometries;
 3 
 4 namespace SharpMap.Utilities
 5 {
 6     /// <summary>
 7     /// Class for transforming between world and image coordinate
 8     /// </summary>
 9     public class Transform
10     {
11         /// <summary>
12         /// Transforms from world coordinate system (WCS) to image coordinates
13         /// 将世界坐标转换为image坐标
14         /// NOTE: This method DOES NOT take the MapTransform property into account (use <see cref="Map.WorldToImage(GeoAPI.Geometries.Coordinate,bool)"/> instead)
15         /// </summary>
16         /// <param name="p">Point in WCS</param>
17         /// <param name="map">Map reference</param>
18         /// <returns>Point in image coordinates</returns>
19         public static PointF WorldtoMap(Coordinate p, Map map)
20         {
21             //if (map.MapTransform != null && !map.MapTransform.IsIdentity)
22             //    map.MapTransform.TransformPoints(new System.Drawing.PointF[] { p });
23             if (p.IsEmpty())
24                 return PointF.Empty;
25 
26             var result = new PointF();
27 
28             var height = (map.Zoom * map.Size.Height) / map.Size.Width;
29             var left = map.Center.X - map.Zoom * 0.5;
30             var top = map.Center.Y + height * 0.5 * map.PixelAspectRatio;
31             result.X = (float)((p.X - left) / map.PixelWidth);
32             result.Y = (float)((top - p.Y) / map.PixelHeight);
33             if (double.IsNaN(result.X) || double.IsNaN(result.Y))
34                 result = PointF.Empty;
35             return result;
36         }
37 
38         /// <summary>
39         /// Transforms from image coordinates to world coordinate system (WCS).
40         /// NOTE: This method DOES NOT take the MapTransform property into account (use <see cref="Map.ImageToWorld(System.Drawing.PointF,bool)"/> instead)
41         /// </summary>
42         /// <param name="p">Point in image coordinate system</param>
43         /// <param name="map">Map reference</param>
44         /// <returns>Point in WCS</returns>
45         public static Coordinate MapToWorld(PointF p, Map map)
46         {
47             if (map.Center.IsEmpty() || double.IsNaN(map.MapHeight))
48             {
49                 return new Coordinate(0, 0);
50             }
51             var ul = new Coordinate(map.Center.X - map.Zoom * .5, map.Center.Y + map.MapHeight * .5);
52             return new Coordinate(ul.X + p.X * map.PixelWidth,
53                                   ul.Y - p.Y * map.PixelHeight);
54         }
55     }
56 }

Transform

详细分析: http://www.cnblogs.com/yhlx125/archive/2012/02/10/2342282.html

2. OpenS-CAD中的实现

已知屏幕分辨率每英寸像素点数，一般为96dpi，定义float m_screenResolution = 96;

1. 初始化CanvasCtrl时，首先调用OnResize()方法。

 1 protected override void OnResize(EventArgs e)
 2         {
 3             base.OnResize(e);
 4 
 5             if (m_lastCenterPoint != UnitPoint.Empty && Width != 0)
 6                 SetCenterScreen(ToScreen(m_lastCenterPoint), false);
 7             m_lastCenterPoint = CenterPointUnit();
 8             m_staticImage = null;
 9             DoInvalidate(true);
10         }

OnResize