导出透明背景色图片

<P>透明原理：将TransparentColor属性的RGB设置为地图背景色一样的值，2个颜色叠加，得到透明效果</P><P>Private Sub UIBtnCtl_ExportPNG_Click()<BR>On Error GoTo PROC_ERROR<BR>    Dim pMxDocument As IMxDocument<BR>    Dim pMap As IMap<BR>    <BR>    Set pMxDocument = Application.Document<BR>    Set pMap = pMxDocument.FocusMap<BR>    <BR>    Dim pAv As IActiveView<BR>    Set pAv = pMap<BR>    Dim pExport As IExport<BR>    Set pExport = New ExportPNG<BR>    Dim pPngExport As IExportPNG<BR>    Set pPngExport = New ExportPNG<BR>    pPngExport.TransparentColor.RGB = RGB(192, 230, 250)<BR>    pPngExport.TransparentColor.Transparency = 0<BR>    pPngExport.TransparentColor.NullColor = False<BR>    Set pExport = pPngExport<BR>    <BR>    Dim pSavePath As String<BR>    pSavePath = "c:/pic.png"<BR>    Dim exportFrame As tagRECT<BR>    exportFrame = pAv.exportFrame<BR>    Dim hdc;, dpi;<BR>    Dim pEnv As IEnvelope<BR>    Set pEnv = New Envelope<BR>    pEnv.PutCoords exportFrame.Left, exportFrame.Top, exportFrame.Right, exportFrame.bottom<BR>    <BR>    dpi = CLng(pExport.Resolution)<BR>    pExport.PixelBounds = pEnv<BR>    pExport.ExportFileName = pSavePath<BR>    pExport.Resolution = dpi<BR>    <BR>    hdc = pExport.StartExporting<BR>    pAv.Output hdc, dpi, exportFrame, Nothing, Nothing<BR>    pExport.FinishExporting<BR>    MsgBox "导出完毕！"<BR>    <BR>    Exit Sub<BR>PROC_ERROR:<BR>    MsgBox Err.Description<BR>End Sub<BR><BR></P>

<P>呵呵，不错，搜藏了          </P>

<P><STRONG>导出透明背景色图片</STRONG><BR></P>
<P>是什么意思，这样得到什么效果？</P>

早贴出来嘛，害得我自己研究两周才搞出来