第五讲MO图形的绘制

1、第五讲 MO图形的绘制 MO虽然不是绘图软件，但经常要用到在地图上画点标明位置，画矩形或多边形标明地图查询范围等操作，因此也需要用到一些基本的绘图功能。MO的绘图就是在MAP上产生图形对象的过程，图形对象主要有：Point（点），Points（点集）、Line（线）、Rectangle（矩形）、Polygon（多边形）、Ellipse（椭圆）。绘图时，先要创建一个绘图对象，给他赋值（位置和尺寸），再在Symbol对象中定义显示方式，最后用Drawshape方法在地图上显示这个图形。定义Symbol对象，不仅可以设置线型、填充方式、尺寸、颜色和字体等，还可以画出多种预定义的符号。Drawshap

2、e方法绘图外，还可以用AddEvent方法在动态图层上画动态图形对象（GeoEvent）。另外还可以用DrawText方法在地图上写字。一、DrawShape绘图方法1、DrawShape定义DrawShape方法的语法为：object.DrawShape shape, symbol其中，object：为绘图目的对象，一般为Map对象；shape：为绘图内容，是图形对象（Point, Points, Line, Rectangle, Polygon or Ellipse）或记录集（Recordset）对象；symbol：是一个Symbol对象，说明绘图方式。注意：调用DrawShape必须在L

3、AYER或TrackingLayer的drawing事件中，即AfterTrackingLayerDraw，BeforeLayerDraw，BeforeTrackingLayerDraw，AfterLayerDraw事件过程中才有效。如果指定一个Recordset作为DrawShape的参数，该数据集必须是从GeoDataset获取，而不是从一个Table对象获取，同时MO从shape字段的第一个特征值开始，到最后一个结束，然后又指向第一个记录。2、画点（1）预定义画点：可以用Point对象画一个点，也可以用Points对象画多个点。示例：Dim sym As New MapObjects2.

4、SymbolDim p As PointDim pts As PointsPrivate Sub Map1_AfterTrackingLayerDraw(ByVal hDC As stdole.OLE_HANDLE) Set pts = New Points Set p = Map1.ToMapPoint(1000, 1000) pts.Add p是Points对象中的一个函数，功能是增加一个Point成员到Points对象内。 Set p = Map1.ToMapPoint(3000, 2000) pts.Add p sym.Color = moRed sym.SymbolType = mo

5、PointSymbol sym.Size = 3 Map1.DrawShape pts, symEnd Sub（2）利用鼠标点击画点：通过鼠标点击屏幕获取点的坐标，进行画点操作。示例：Dim sym As New MapObjects2.SymbolDim p As PointDim pts As New PointsPrivate Sub Map1_AfterTrackingLayerDraw(ByVal hDC As stdole.OLE_HANDLE) If Not pts Is Nothing Then sym.Color = moRed sym.SymbolType = moPoin

6、tSymbol sym.Size = 3 Map1.DrawShape pts, sym Map1.DrawShape pts, sym End IfEnd SubPrivate Sub Map1_MouseDown(Button As Integer, Shift As Integer, X As Single, Y As Single) Set p = Map1.ToMapPoint(X, Y) pts.Add p Map1.TrackingLayer.Refresh True TrackingLayer对象是MAP控件中的一个图层，它描述位置可以动态改变的地理目标，Refresh是Tra

7、ckingLayer对象的成员函数，强制刷新TrackingLayer对象。End Sub3、画线MO中画线的基本原理是先设置两个点，将他们添加到一个Points对象中，再将Points对象放到一个Line对象中，使用DrawShape方法就可以画出一条线段来。如果在Points对象中有N个点，则可以产生一条N-1段的折线。（1）预定义点画线，示例：Dim g_line As MapObjects2.LineDim pts As PointsDim p As PointDim sym As SymbolPrivate Sub Command1_Click()Set g_line = New M

8、apObjects2.LineSet pts = New PointsSet p = Map1.ToMapPoint(1000, 1000)pts.Add pSet p = Map1.ToMapPoint(2000, 3000)pts.Add pg_line.Parts.Add pts Parts是Line对象的一个属性，此属性指向一个Parts集合对象，通过Parts属性可以检索组成线的片断（Parts），而Parts的每一个成员是一个点集（Points）。Set pts = g_line.Parts(0)Map1.RefreshEnd SubPrivate Sub Map1_AfterTr

9、ackingLayerDraw(ByVal hDC As stdole.OLE_HANDLE)If Not g_line Is Nothing ThenDim sym As New SymbolIf pts.Count 1 Then Count属性表示当前Points对象内成员的数目，这是一个只读值。sym.Color = moRedsym.SymbolType = moLineSymbolsym.Size = 5Map1.DrawShape g_line, symEnd IfEnd IfEnd Sub（2）鼠标点击获取点并画线，示例：Dim g_line As MapObjects2.Lin

10、eDim pts As PointsDim p As PointDim sym As SymbolPrivate Sub Command1_Click()设置清空按钮Set g_line = NothingSet pts = NothingMap1.RefreshEnd SubPrivate Sub Map1_AfterTrackingLayerDraw(ByVal hDC As stdole.OLE_HANDLE)Dim sym As New SymbolIf Not g_line Is Nothing Thensym.Color = moBlackMap1.DrawShape pts, s

11、ymIf pts.Count 1 Thensym.Color = moRedsym.SymbolType = moLineSymbolsym.Size = 5Map1.DrawShape g_line, symEnd IfEnd IfEnd SubPrivate Sub Map1_MouseDown(Button As Integer, Shift As Integer, X As Single, Y As Single)If Button = 1 ThenIf g_line Is Nothing ThenSet g_line = New MapObjects2.LineEnd IfIf pt

12、s Is Nothing ThenSet pts = New PointsEnd IfSet p = Map1.ToMapPoint(X, Y)pts.Add pIf pts.Count = 1 Theng_line.Parts.Add ptsSet pts = g_line.Parts(0)End IfMap1.TrackingLayer.Refresh TrueElseMsgBox rightEnd IfEnd Sub4、画矩形和椭圆（1）预定义画矩形：画矩形是先定义一个矩形对象，给它的top、left、bottom、right属性赋值，再使用DrawShape方法就可以画出一个矩形来。定

13、义矩形范围时，可以先确定一个中心点，再确定一个半径（或X方向半径和Y方向半径），得到top、left、bottom、right的值。示例：Option ExplicitDim rect As MapObjects2.RectanglePrivate Sub Command1_Click()Dim dist As DoubleDim pt As New PointSet rect = New MapObjects2.Rectangledist = 0.2Set pt = Map1.ToMapPoint(2500, 1500)这里可以动态设置中心点的位置rect.Right = pt.X + di

14、strect.Left = pt.X - distrect.Top = pt.Y + distrect.Bottom = pt.Y - distMap1.RefreshEnd SubPrivate Sub Map1_AfterTrackingLayerDraw(ByVal hDC As stdole.OLE_HANDLE)If Not rect Is Nothing ThenDim sym As New Symbolsym.SymbolType = moFillSymbolsym.Style = moDiagonalCrossFillsym.Color = moBlueMap1.DrawSha

15、pe rect, symEnd IfEnd Sub（2）定义一个矩形框对象后，进行画矩形。示例：Option ExplicitDim rect As MapObjects2.RectanglePrivate Sub Map1_AfterTrackingLayerDraw(ByVal hDC As stdole.OLE_HANDLE) Dim sym As New MapObjects2.Symbol If Not rect Is Nothing Then sym.SymbolType = moFillSymbol sym.Style = moDiagonalCrossFill sym.Colo

16、r = moBlue Map1.DrawShape rect, sym End IfEnd SubPrivate Sub Map1_MouseDown(Button As Integer, Shift As Integer, X As Single, Y As Single) Set rect = Map1.TrackRectangle Map1.TrackingLayer.Refresh TrueEnd Sub用同样的方法可以画出椭圆来。5、用Track方法画图形在MO中还可以用一类方法在地图上半自动画图，如：TrackCircle方法，点击产生圆心，拖动产生半径，放手成圆形；TrackRe

17、ctangle方法，点击产生一个角，拖动放大，放手形成矩形；TrackPolygon方法，点击画几条直线，双击形成多边形图形。这一类方法都是以Track开头，所以称为Track画图方法，这和TrackingLayer（动态图层）毫无关系。示例：Option ExplicitDim eli As MapObjects2.EllipseDim recs As MapObjects2.RectangleDim ply As MapObjects2.PolygonPrivate Sub Map1_AfterTrackingLayerDraw(ByVal hDC As stdole.OLE_HANDLE

18、) Dim sym As New MapObjects2.Symbol sym.SymbolType = moFillSymbol sym.Style = moDiagonalCrossFill If Not recs Is Nothing Then sym.Color = moBlue Map1.DrawShape recs, sym End If If Not eli Is Nothing Then sym.Color = moRed Map1.DrawShape eli, sym End If If Not ply Is Nothing Then sym.Color = moGreen

19、Map1.DrawShape ply, sym End IfEnd SubPrivate Sub Map1_MouseDown(Button As Integer, Shift As Integer, X As Single, Y As Single) If Option1 Then Set recs = Map1.TrackRectangle ElseIf Option2 Then Set eli = Map1.TrackCircle Else Set ply = Map1.TrackPolygon End If Map1.TrackingLayer.Refresh TrueEnd Sub二

20、、写文字MO一般采用DrawText方法在地图上写文字，也可以用画点时的motruetypemarker方式，在地图上写各种地图上常用的符号。1、DrawText方法用DrawText方法可以在地图上写文字，语法结构为：object.DrawText text, shape, symbol其中，object：对象，text：字符串，shape：参照图形，可以是点、点集、线和矩形；symbol：为一个Textsymbol显示对象。如果参照图形为点，则文字中心在点上；如果为点集，则中心在点集的范围中心上；为直线，中心在线段的中心上，方向同线段的方向；为折线，则文字的中心和方向按照点集的样条插值计算

21、；如果为矩形，则文字国矩形中心的水平线排列。（1）在点击出写文字示例：Option ExplicitDim p As MapObjects2.PointDim tSym As New TextSymbolPrivate Sub Map1_AfterTrackingLayerDraw(ByVal hDC As stdole.OLE_HANDLE)If Not p Is Nothing Then Dim sym As New Symbol tSym.Color = moRedMap1.DrawText Text1.Text, p, tSymEnd IfEnd SubPrivate Sub Map1

22、_MouseDown(Button As Integer, Shift As Integer, x As Single, y As Single) Set p = Map1.ToMapPoint(x, y)Map1.TrackingLayer.Refresh TrueEnd Sub（2）在线段上添加文字示例：Option ExplicitDim g_line As MapObjects2.LineDim pts As MapObjects2.PointsPrivate Sub Map1_AfterTrackingLayerDraw(ByVal hDC As stdole.OLE_HANDLE)

23、 make sure theres a line If Not g_line Is Nothing Then make sure theres at least two points in the line If pts.Count 1 Then Dim tSym As New TextSymbol use the font of the textbox control Set tSym.Font = Text1.Font Dim sym As New Symbol sym.Color = moRed Map1.DrawShape g_line, sym Map1.DrawText Text1

24、.Text, g_line, tSym End If End IfEnd SubPrivate Sub Map1_MouseDown(Button As Integer, Shift As Integer, x As Single, y As Single) If Button = 1 Then create the line if it does not exist If g_line Is Nothing Then Set g_line = New MapObjects2.Line End If If pts Is Nothing Then Set pts = New MapObjects

25、2.Points End If create a point and add it to the line Dim p As Point Set p = Map1.ToMapPoint(x, y) pts.Add p If pts.Count = 1 Then g_line.Parts.Add pts Set pts = g_line.Parts(0) End If refresh the trackingLayer Map1.TrackingLayer.Refresh True Else Dim r As MapObjects2.Rectangle Set r = Map1.TrackRec

26、tangle If Not r Is Nothing Then Map1.Extent = r End IfEnd Sub三、SymbolSymbol是控制地图上的特征或图形的显示方式的对象或属性，图上的特征都是通过设置图层的Symbol属性来实现的，如：layer.Symbol.Color = moRed，如果没有设置图层的Symbol属性，MO就会使用缺省的线型、填充方式、尺寸、字体和随机的颜色。在设置图形的显示方式时，要定义一个Symbol对象：Dim sym As New Symbol再设置SymbolType属性，这说明显示对象是点、线还是面，使用的常量如下：Constant Val

27、ue DescriptionmoPointSymbol0symbol for a Point or Points objectmoLineSymbol1symbol for a Line objectmoFillSymbol2symbols for a Polygon, Rectangle or Ellipse object例如：sym.SymbolType = moFillSymbol然后就可以设置Symbol的style属性，对于点来设置点的形状和预定义的符号，对于线对象来设置线型，对于面对象来设置填充方式。最后来设置size、color、font等。使用预定义符号：在画点时，设置Symb

28、ol的style属性为moTrueTypeMarker方式，可以在地图上写各种地图上常用的符号，先设置：sym.Style = moTrueTypeMarker，然后再设置sym.CharacterIndex = 35。CharacterIndex的序号是从33开始的。下面就是一个使用预定义字符的例子：Option ExplicitDim Pt(400) As MapObjects2.PointDim Pt1(400) As MapObjects2.PointDim Sym(400) As New MapObjects2.SymbolDim tSym As New MapObjects2.Te

29、xtSymbolPrivate Sub Form_Load() Dim i As Integer Dim Swidth As Integer Dim Sheight As Integer Swidth = Screen.Width Sheight = Screen.Height Swidth = 800 * 15 Sheight = 600 * 15 Me.Height = Sheight - 100 Me.Width = Swidth - 300 Map1.Height = Me.Height - 200 Map1.Width = Me.Width - 200 Map1.Top = 100

30、Map1.Left = 100 For i = 0 To 399 With Sym(i) .Style = moTrueTypeMarker .SymbolType = moPointSymbol .Font = ESRI Transportation & Municipal .Size = 20 .Style = moTrueTypeMarker .Color = moBlack End With Next i tSym.Color = moBlack tSym.Font.Size = 10 End SubPrivate Sub Map1_AfterTrackingLayerDraw(ByV

31、al hDC As stdole.OLE_HANDLE) Dim i As Integer For i = 0 To 399 If Not Pt(i) Is Nothing Then Map1.DrawShape Pt(i), Sym(i) Map1.DrawText 33 + i, Pt1(i), tSym End If Next iEnd SubPrivate Sub Map1_Click() Dim i As Integer, j As Integer, k As Integer Const Mx0 = 400 Const My0 = 300 Const Mxc = 520 Const

32、Myc = 800 k = 0 j = 0 For i = 0 To 199 For i = 200 To 399 Set Pt(i) = Map1.ToMapPoint(j * Mxc + Mx0, My0 + k * Myc) Set Pt1(i) = Map1.ToMapPoint(j * Mxc + Mx0, My0 + 400 + k * Myc) Sym(i).CharacterIndex = 33 + i j = j + 1 If j = 20 Then j = 0 k = k + 1 End If Next i Map1.TrackingLayer.Refresh TrueEn

33、d Sub画出交通和市政的预定义符号，符号代码如下：Option ExplicitDim Pt(400) As MapObjects2.PointDim Pt1(400) As MapObjects2.PointDim Sym(400) As New MapObjects2.SymbolDim tSym As New MapObjects2.TextSymbolPrivate Sub Form_Load() Dim i As Integer Dim Swidth As Integer Dim Sheight As Integer Dim fnt As New StdFont fnt.Name = Wingdings Swidth = Screen.Wid