[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：

 using System.Drawing;

 using GeoAPI.Geometries;

 namespace SharpMap.Utilities

 {

     /// <summary>

     /// Class for transforming between world and image coordinate

     /// </summary>

     public class Transform

     {

         /// <summary>

         /// Transforms from world coordinate system (WCS) to image coordinates

         /// 将世界坐标转换为image坐标

         /// NOTE: This method DOES NOT take the MapTransform property into account (use <see cref="Map.WorldToImage(GeoAPI.Geometries.Coordinate,bool)"/> instead)

         /// </summary>

         /// <param name="p">Point in WCS</param>

         /// <param name="map">Map reference</param>

         /// <returns>Point in image coordinates</returns>

         public static PointF WorldtoMap(Coordinate p, Map map)

         {

             //if (map.MapTransform != null && !map.MapTransform.IsIdentity)

             //    map.MapTransform.TransformPoints(new System.Drawing.PointF[] { p });

             if (p.IsEmpty())

                 return PointF.Empty;

             var result = new PointF();

             var height = (map.Zoom * map.Size.Height) / map.Size.Width;

             var left = map.Center.X - map.Zoom * 0.5;

             var top = map.Center.Y + height * 0.5 * map.PixelAspectRatio;

             result.X = (float)((p.X - left) / map.PixelWidth);

             result.Y = (float)((top - p.Y) / map.PixelHeight);

             if (double.IsNaN(result.X) || double.IsNaN(result.Y))

                 result = PointF.Empty;

             return result;

         }

         /// <summary>

         /// Transforms from image coordinates to world coordinate system (WCS).

         /// NOTE: This method DOES NOT take the MapTransform property into account (use <see cref="Map.ImageToWorld(System.Drawing.PointF,bool)"/> instead)

         /// </summary>

         /// <param name="p">Point in image coordinate system</param>

         /// <param name="map">Map reference</param>

         /// <returns>Point in WCS</returns>

         public static Coordinate MapToWorld(PointF p, Map map)

         {

             if (map.Center.IsEmpty() || double.IsNaN(map.MapHeight))

             {

                 return new Coordinate(, );

             }

             var ul = new Coordinate(map.Center.X - map.Zoom * ., map.Center.Y + map.MapHeight * .);

             return new Coordinate(ul.X + p.X * map.PixelWidth,

                                   ul.Y - p.Y * map.PixelHeight);

         }

     }

 }

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。

 protected override void OnResize(EventArgs e)

         {

             base.OnResize(e);

             if (m_lastCenterPoint != UnitPoint.Empty && Width != )

                 SetCenterScreen(ToScreen(m_lastCenterPoint), false);

             m_lastCenterPoint = CenterPointUnit();

             m_staticImage = null;

             DoInvalidate(true);

         }

OnResize

由于m_lastCenterPoint是结构体变量，所以首先设置到中心点m_lastCenterPoint，即(0,0)，是Unit坐标

if (m_lastCenterPoint != UnitPoint.Empty && Width != 0)
SetCenterScreen(ToScreen(m_lastCenterPoint), false);

接着调用m_lastCenterPoint = CenterPointUnit();

通过直角坐标的左上角点和右下角点计算。其实初始化时候执行该方法没有起到设置基准点的作用。可以跳过这2次，等窗体Resize的时候再看。

 public UnitPoint CenterPointUnit()

         {

             UnitPoint p1 = ScreenTopLeftToUnitPoint();

             UnitPoint p2 = ScreenBottomRightToUnitPoint();

             UnitPoint center = new UnitPoint();

             center.X = (p1.X + p2.X) / ;

             center.Y = (p1.Y + p2.Y) / ;

             return center;

         }

         public UnitPoint ScreenTopLeftToUnitPoint()

         {

             return ToUnit(new PointF(, ));

         }

         public UnitPoint ScreenBottomRightToUnitPoint()

         {

             return ToUnit(new PointF(this.ClientRectangle.Width, this.ClientRectangle.Height));

         }

CenterPointUnit

2. 接着打开文档DocumentForm，在构造的过程中设置文档画布的视点中心坐标为（0,0）。这样就实现了绘图画布原点坐标和屏幕（客户区）中心点的对应，形成基准点。默认的数据的长度单位为inch，屏幕坐标的单位为像素。这两者之间存在比例关系，通过Zoom缩放比例来实现尺度的变换，同时结合平移量和偏移距离计算出鼠标点的世界坐标。

m_canvas.SetCenter(new UnitPoint(0, 0));

或者加载完数据，设置画布的视点中心坐标。

m_canvas.SetCenter(m_data.CenterPoint);

 public DocumentForm(string filename)

         {

             InitializeComponent();

             Text = "<New Document>";

             m_data = new DataModel();

             if (filename.Length >  && File.Exists(filename) && m_data.Load(filename))

             {

                 Text = filename;

                 m_filename = filename;

             }

             m_canvas = new CanvasCtrl(this, m_data);

             m_canvas.Dock = DockStyle.Fill;

             Controls.Add(m_canvas);

             m_canvas.SetCenter(new UnitPoint(, ));

             m_canvas.RunningSnaps = new Type[]

                 {

                 typeof(VertextSnapPoint),

                 typeof(MidpointSnapPoint),

                 typeof(IntersectSnapPoint),

                 typeof(QuadrantSnapPoint),

                 typeof(CenterSnapPoint),

                 typeof(DivisionSnapPoint),

                 };

             m_canvas.AddQuickSnapType(Keys.N, typeof(NearestSnapPoint));

             m_canvas.AddQuickSnapType(Keys.M, typeof(MidpointSnapPoint));

             m_canvas.AddQuickSnapType(Keys.I, typeof(IntersectSnapPoint));

             m_canvas.AddQuickSnapType(Keys.V, typeof(VertextSnapPoint));

             m_canvas.AddQuickSnapType(Keys.P, typeof(PerpendicularSnapPoint));

             m_canvas.AddQuickSnapType(Keys.Q, typeof(QuadrantSnapPoint));

             m_canvas.AddQuickSnapType(Keys.C, typeof(CenterSnapPoint));

             m_canvas.AddQuickSnapType(Keys.T, typeof(TangentSnapPoint));

             m_canvas.AddQuickSnapType(Keys.D, typeof(DivisionSnapPoint));

             m_canvas.KeyDown += new KeyEventHandler(OnCanvasKeyDown);

             SetupMenuItems();

             SetupDrawTools();

             SetupLayerToolstrip();

             SetupEditTools();

             UpdateLayerUI();

             MenuStrip menuitem = new MenuStrip();//创建文档的主菜单

             menuitem.Items.Add(m_menuItems.GetMenuStrip("edit"));

             menuitem.Items.Add(m_menuItems.GetMenuStrip("draw"));

             menuitem.Visible = false;

             Controls.Add(menuitem);

             this.MainMenuStrip = menuitem;

         }

         protected override void OnLoad(EventArgs e)

         {

             base.OnLoad(e);

             m_canvas.SetCenter(m_data.CenterPoint);

         }

　　2.1查看SetCenter(UnitPoint unitPoint)方法，首先调用PointF point = ToScreen(unitPoint);将unitPoint转换PointF point.找到地图原点对应的屏幕坐标，应该是屏幕左下角点偏移(25,-25)。

         /// <summary>

         /// 设置画布到屏幕的中心

         /// </summary>

         /// <param name="rPoint">直角坐标系坐标</param>

         public void SetCenter(RPoint unitPoint)

         {

             //将unitPoint点对应到屏幕上point

             PointF point = Transform.ToScreen(unitPoint, this);

             m_lastCenterPoint = unitPoint;

             //将unitPoint偏移到屏幕中心

             SetCenterScreen(point, false);

         }

SetCenter

　这里注意计算Unit坐标到屏幕坐标的ToScreen()方法中，transformedPoint.Y = ScreenHeight() - transformedPoint.Y;//将Unit坐标系转换为屏幕坐标系，Y轴反向

　其中ScreenHeight()方法似乎有点问题，修改后如下。

  /// <summary>

         /// 将Unit坐标转换到屏幕坐标

         /// </summary>

         /// <param name="point"></param>

         /// <returns></returns>

         public PointF ToScreen(UnitPoint point)

         {

             PointF transformedPoint = Translate(point);

             transformedPoint.Y = ScreenHeight() - transformedPoint.Y;//将Unit坐标系转换为屏幕坐标系，Y轴反向

             transformedPoint.Y *= m_screenResolution * m_model.Zoom;

             transformedPoint.X *= m_screenResolution * m_model.Zoom;

             transformedPoint.X += m_panOffset.X + m_dragOffset.X;

             transformedPoint.Y += m_panOffset.Y + m_dragOffset.Y;

             return transformedPoint;

         }

ToScreen

 float ScreenHeight()

         {

             return (float)(ToUnit(this.ClientRectangle.Height));

             //return (float)(ToUnit(this.ClientRectangle.Height) / m_model.Zoom);

         }

ScreenHeight

　　这样就引出了ToUnit(float screenvalue)函数，将屏幕距离转换为英寸数。

 public double ToUnit(float screenvalue)

         {

             return (double)screenvalue / (double)(m_screenResolution * m_model.Zoom);

         }

3. 接着将unitPoint赋值给m_lastCenterPoint

m_lastCenterPoint = unitPoint;

SetCenterScreen(point, false);

调用了SetCenterScreen()方法，

 protected  void SetCenterScreen(PointF screenPoint, bool setCursor)

         {

             float centerX = ClientRectangle.Width / ;

             m_panOffset.X += centerX - screenPoint.X;

             float centerY = ClientRectangle.Height / ;

             m_panOffset.Y += centerY - screenPoint.Y;

             if (setCursor)

                 Cursor.Position = this.PointToScreen(new Point((int)centerX, (int)centerY));

             DoInvalidate(true);

         }

4.理解了public PointF ToScreen(UnitPoint point)，那public UnitPoint ToUnit(PointF screenpoint)也好理解了。

  /// <summary>

         ///  将屏幕坐标转换到Unit坐标

         /// </summary>

         /// <param name="screenpoint"></param>

         /// <returns></returns>

         public UnitPoint ToUnit(PointF screenpoint)

         {

             float panoffsetX = m_panOffset.X + m_dragOffset.X;

             float panoffsetY = m_panOffset.Y + m_dragOffset.Y;

             float xpos = (screenpoint.X - panoffsetX) / (m_screenResolution * m_model.Zoom);

             float ypos = ScreenHeight() - ((screenpoint.Y - panoffsetY)) / (m_screenResolution * m_model.Zoom);

             return new UnitPoint(xpos, ypos);

         }

ToUnit

5.最后单独说一下ToScreen(UnitPoint point)和ToUnit(PointF screenpoint)中的两个变量

PointF m_panOffset = new PointF(, -);

PointF m_dragOffset = new PointF(, );

这里m_panOffset控制的是中心点Center的偏移量，是一个累计的量，相对于中心点。

m_dragOffset记录了每次移动过程中的移动量，每次产生一个新值。每次CanvasCtrl控件的OnMouseDown时累积到偏移量上，之后重新初始化，同时在OnMouseUp时的移动命令下重新初始化（如下代码），似乎重复了。

 if (m_commandType == eCommandType.pan)

             {

                 m_panOffset.X += m_dragOffset.X;

                 m_panOffset.Y += m_dragOffset.Y;

                 m_dragOffset = new PointF(, );

             }

在protected override void OnMouseMove(MouseEventArgs e)事件中

 if (m_commandType == eCommandType.pan && e.Button == MouseButtons.Left)

             {

                 m_dragOffset.X = -(m_mousedownPoint.X - e.X);

                 m_dragOffset.Y = -(m_mousedownPoint.Y - e.Y);

                 m_lastCenterPoint = CenterPointUnit();

                 DoInvalidate(true);

             }

可知，m_dragOffset和m_panOffset记录的是偏移的屏幕坐标。

巴特西

[SharpMap] 屏幕坐标和Map坐标转换

最新文章

热门文章