将symbologycontrol中选中的symbol或对象转化为图像

当我们用Symbologycontrol设置某个图层symbol的样式或设置指北针、比例尺的样式时，我们需要将这些选中的样式以图片的形式显示在例如PictureBox中，这时我们就需要得到选中对象的Image，下面是我提供的两种方法：

一：是利用AE自带的PreviewItem方法来实现，这种方法普适性好，能适用所有Symbolgycontrol支持的对象

二：是利用Symbol的Draw函数实现，该方法目前只支持Symbol，可以进行扩充

方法一：

''' <summary>
  ''' 通过SymbolObject获得image
  ''' </summary>
  ''' <param name="pStyleGallery">传入的Symbologycontrol中选中的项</param>
  ''' <param name="pStyleClass">当前类型</param>
  ''' <param name="pWidth">图像宽度</param>
  ''' <param name="pHeight">图像高度</param>
  ''' <returns>得到的Image</returns>
  ''' <remarks></remarks>
  Shared Function GetImageFromSymbolObject(ByVal pStyleGallery As IStyleGalleryItem, ByVal pStyleClass As esriSymbologyStyleClass, ByVal pWidth As Double, ByVal pHeight As Double) As Image
    Dim pSymbology As ISymbologyControl = New SymbologyControl
    pSymbology.StyleClass = pStyleClass
    pSymbology.GetStyleClass(pSymbology.StyleClass).AddItem(pStyleGallery, 0)
    Dim picture As stdole.IPictureDisp = pSymbology.GetStyleClass(pSymbology.StyleClass).PreviewItem(pStyleGallery, pWidth, pHeight)
    Dim image As System.Drawing.Image = System.Drawing.Image.FromHbitmap(New System.IntPtr(picture.Handle))
    Return image
  End Function
  ''' <summary>
  ''' 通过SymbolObject获得image
  ''' </summary>
  ''' <param name="pSymbology">传入的symbologycontrol</param>
  ''' <param name="pStyleGallery">传入的Symbologycontrol中选中的项</param>
  ''' <param name="pWidth">图像宽度</param>
  ''' <param name="pHeight">图像高度</param>
  ''' <returns>得到的Image</returns>
  ''' <remarks></remarks>
  Shared Function GetImageFromSymbolObject(ByVal pSymbology As ISymbologyControl, ByVal pStyleGallery As IStyleGalleryItem, ByVal pWidth As Double, ByVal pHeight As Double) As Image
    Dim picture As stdole.IPictureDisp = pSymbology.GetStyleClass(pSymbology.StyleClass).PreviewItem(pStyleGallery, pWidth, pHeight)
    Dim image As System.Drawing.Image = System.Drawing.Image.FromHbitmap(New System.IntPtr(picture.Handle))
    Return image
  End Function
  ''' <summary>
  ''' 通过SymbolObject获得image
  ''' </summary>
  ''' <param name="pStyleClass">当前的类型</param>
  ''' <param name="pSymbolObject">传入的对象，比如TextSymbol，NorthArrow</param>
  ''' <param name="pWidth">图像宽度</param>
  ''' <param name="pHeight">图像高度</param>
  ''' <returns>得到的Image</returns>
  ''' <remarks></remarks>
  Shared Function GetImageFromSymbolObject(ByVal pStyleClass As esriSymbologyStyleClass, ByVal pSymbolObject As Object, ByVal pWidth As Double, ByVal pHeight As Double) As Image
    Dim pSymbology As ISymbologyControl = New SymbologyControl
    Dim pStyleGallery As IStyleGalleryItem = New ServerStyleGalleryItem
    pStyleGallery.Name = "当前符号"
    pStyleGallery.Item = pSymbolObject
    pSymbology.GetStyleClass(pStyleClass).AddItem(pStyleGallery, 0)
    Dim picture As stdole.IPictureDisp = pSymbology.GetStyleClass(pStyleClass).PreviewItem(pStyleGallery, pWidth, pHeight)
    Dim image As System.Drawing.Image = System.Drawing.Image.FromHbitmap(New System.IntPtr(picture.Handle))
    Return image
  End Function
  ''' <summary>
  ''' 通过SymbolObject获得image
  ''' </summary>
  ''' <param name="pSymbolObject">传入的对象，比如TextSymbol，NorthArrow</param>
  ''' <param name="pWidth">图像宽度</param>
  ''' <param name="pHeight">图像高度</param>
  ''' <returns>得到的Image</returns>
  ''' <remarks></remarks>
  Shared Function GetImageFromSymbolObject(ByVal pSymbolObject As Object, ByVal pWidth As Double, ByVal pHeight As Double) As Image
    Dim pSymbology As ISymbologyControl = New SymbologyControl
    Dim pStyleGallery As IStyleGalleryItem = New ServerStyleGalleryItem
    pStyleGallery.Name = "当前符号"
    pStyleGallery.Item = pSymbolObject
    Dim pStyleClass As esriSymbologyStyleClass = GetStyleClass(pSymbolObject)
    pSymbology.GetStyleClass(pStyleClass).AddItem(pStyleGallery, 0)
    Dim picture As stdole.IPictureDisp = pSymbology.GetStyleClass(pStyleClass).PreviewItem(pStyleGallery, pWidth, pHeight)
    Dim image As System.Drawing.Image = System.Drawing.Image.FromHbitmap(New System.IntPtr(picture.Handle))
    Return image
  End Function

  ''' <summary>
  ''' 获得当前对应的styleclass
  ''' </summary>
  ''' <param name="pSymbolObject">当前的对象</param>
  ''' <returns></returns>
  ''' <remarks></remarks>
  Shared Function GetStyleClass(ByVal pSymbolObject As Object) As esriSymbologyStyleClass
    If TypeOf pSymbolObject Is ITextSymbol Then
      Return esriSymbologyStyleClass.esriStyleClassTextSymbols
    ElseIf TypeOf pSymbolObject Is IMarkerSymbol Then
      Return esriSymbologyStyleClass.esriStyleClassMarkerSymbols
    ElseIf TypeOf pSymbolObject Is ILineSymbol Then
      Return esriSymbologyStyleClass.esriStyleClassLineSymbols
    ElseIf TypeOf pSymbolObject Is IFillSymbol Then
      Return esriSymbologyStyleClass.esriStyleClassFillSymbols
    ElseIf TypeOf pSymbolObject Is IScaleText Then
      Return esriSymbologyStyleClass.esriStyleClassScaleTexts
    ElseIf TypeOf pSymbolObject Is IScaleBar Then
      Return esriSymbologyStyleClass.esriStyleClassScaleBars
    ElseIf TypeOf pSymbolObject Is INorthArrow Then
      Return esriSymbologyStyleClass.esriStyleClassNorthArrows
    ElseIf TypeOf pSymbolObject Is IBackground Then
      Return esriSymbologyStyleClass.esriStyleClassBackgrounds
    ElseIf TypeOf pSymbolObject Is IBorder Then
      Return esriSymbologyStyleClass.esriStyleClassBorders
    ElseIf TypeOf pSymbolObject Is IShadow Then
      Return esriSymbologyStyleClass.esriStyleClassLabels
    ElseIf TypeOf pSymbolObject Is ILegend Then
      Return esriSymbologyStyleClass.esriStyleClassLegendItems
    End If
  End Function



方法二：


  ''' <summary>
  ''' 将symbol转成bitmap
  ''' </summary>
  ''' <param name="pSymbol">symbol</param>
  ''' <param name="iwidth">图像宽</param>
  ''' <param name="iheight">图像高</param>
  ''' <returns>返回bitmap</returns>
  ''' <remarks></remarks>
  Shared Function SymbolToBitmp(ByVal pSymbol As ISymbol, ByVal iwidth As Integer, ByVal iheight As Integer) As System.Drawing.Bitmap
    ''根据高宽创建图象
    Dim bmp As Drawing.Bitmap = New Drawing.Bitmap(iwidth, iheight)
    Dim gImage As Drawing.Graphics = Drawing.Graphics.FromImage(bmp)
    gImage.Clear(Drawing.Color.White)

    Dim dpi As Double = gImage.DpiX
    Dim pEnvelope As IEnvelope = New EnvelopeClass()
    pEnvelope.PutCoords(0, 0, bmp.Width, bmp.Height)
    Dim deviceRect As New tagRECT
    deviceRect.left = 0
    deviceRect.right = bmp.Width
    deviceRect.top = 0
    deviceRect.bottom = bmp.Height
    Dim pDisplayTransformation As IDisplayTransformation = New DisplayTransformationClass
    pDisplayTransformation.VisibleBounds = pEnvelope
    pDisplayTransformation.Bounds = pEnvelope
    pDisplayTransformation.DeviceFrame = deviceRect
    pDisplayTransformation.Resolution = dpi

    Dim pGeo As IGeometry = CreateSymShape(pSymbol, pEnvelope)
    Dim hdc As System.IntPtr = New IntPtr()
    hdc = gImage.GetHdc()
    ''将符号的形状绘制到图象中
    pSymbol.SetupDC(hdc, pDisplayTransformation)
    pSymbol.Draw(pGeo)
    pSymbol.ResetDC()
    gImage.ReleaseHdc(hdc)
    gImage.Dispose()
    Return bmp
  End Function

  Shared Function CreateSymShape(ByVal pSymbol As ISymbol, ByVal pEnvelope As IEnvelope) As IGeometry

    Dim pGeo As IGeometry = Nothing
    '' 根据传入的符号以及外包矩形区域返回对应的几何空间实体（点，线、面）
    ''判断是否为“点”符号
    If TypeOf pSymbol Is IMarkerSymbol Then
      Dim pMarkerSym As IMarkerSymbol = pSymbol
      If pMarkerSym IsNot Nothing Then
        ''为“点”符号则返回IEnvelope的中心点
        Dim pArea As IArea = pEnvelope
        pGeo = pArea.Centroid
      End If
    ElseIf TypeOf pSymbol Is ILineSymbol Then
      ''判断是否为“线”符号
      Dim IlineSym As ILineSymbol = pSymbol
      If IlineSym IsNot Nothing Then
        ''返回45度的对角线
        Dim IpLine As IPolyline
        IpLine = New PolylineClass()
        IpLine.FromPoint = pEnvelope.LowerLeft
        IpLine.ToPoint = pEnvelope.UpperRight
        pGeo = IpLine
      End If
    ElseIf TypeOf pSymbol Is IFillSymbol Then
      ''直接返回一个IEnvelope矩形区域
      pGeo = pEnvelope
    End If
    Return pGeo
  End Function

原文出处：http://www.evget.com/zh-CN/Info/ReadInfo.aspx?id=9092