编写一个colorramp下拉框，无非就做两件事，首先将colorramp绘制成一个bitmap图片，其次就是将该图片绘制到combobox的item上。
那么现看看后面一个问题怎么绘制到combobox上：vb.net代码实例
首先在form上加载一个imagelist，将要绘制的图片存放到里面（将以自己截个colorramp的图片），再加载combobox，将其Drawmode设置为owenrdrawfixed，然后在其DrawItem事件中编写
- Private Sub ComboBox1_DrawItem(ByVal sender As Object, ByVal e As System.Windows.Forms.DrawItemEventArgs) Handles ComboBox1.DrawItem
- Dim iRectangle As System.Drawing.Rectangle
- If e.Index = -1 Or sender Is Nothing Then
- Exit Sub
- Else
- '绘制背景
- e.DrawBackground()
- '绘制焦点框
- e.DrawFocusRectangle()
- '绘制图例
- iRectangle = New System.Drawing.Rectangle(e.Bounds.Left + 1, e.Bounds.Top + 1, 117, 14)
- e.Graphics.DrawImage(Me.ImageList1.Images(e.Index), iRectangle)
- End If
- End Sub
复制代码 上面一段代码就可以将imagelist中相应序号的图片绘制到相应序号的item上了，视觉部分完毕，很easy吧？
有了上面的过程我们就应该思考怎么样得到指定colorramp的图像，如果能得到colorramp的图像，只要替换imagelist中的图片就可以实现我们的目的。
注意：下面的代码首先新建一个ESRI.ARCGIS.Display.IGradientFillSymbol和一个ColorRamp
- Private Sub DrawColorRamp()
- '新建 m_FillSymbol和m_ColorRamp
- m_FillSymbol.ColorRamp = m_ColorRamp
- Me.PictureBox1.Image = SymbolToBitmap(m_FillSymbol, 0, Me.PictureBox1.Width, Me.PictureBox1.Height)
- End Sub
复制代码
- Friend Function SymbolToBitmap(ByVal iSymbol As ESRI.ARCGIS.Display.ISymbol, ByVal iStyle As Integer, ByVal iWidth As Integer, ByVal iHeight As Integer) As System.Drawing.Bitmap
- Dim iHDC As New IntPtr
- Dim iBitmap As System.Drawing.Bitmap
- Dim iGraphics As System.Drawing.Graphics
- Dim itagRECT As ESRI.ARCGIS.Display.tagRECT
- Dim iEnvelope As ESRI.ARCGIS.Geometry.IEnvelope
- Dim iDisplayTransformation As ESRI.ARCGIS.Display.IDisplayTransformation
- Dim iPoint As ESRI.ArcGIS.Geometry.IPoint
- Dim iPolyline As ESRI.ArcGIS.Geometry.IGeometryCollection
- Dim iPolygon As ESRI.ArcGIS.Geometry.IGeometryCollection
- Dim iRing As ESRI.ArcGIS.Geometry.IRing
- Dim iSegmentCollection As ESRI.ArcGIS.Geometry.ISegmentCollection
- Dim iGeometry As ESRI.ArcGIS.Geometry.IGeometry
- iBitmap = New System.Drawing.Bitmap(iWidth, iHeight)
- iGraphics = System.Drawing.Graphics.FromImage(iBitmap)
- iEnvelope = New ESRI.ArcGIS.Geometry.Envelope
- iEnvelope.PutCoords(0, 0, iWidth, iHeight)
- With itagRECT
- .left = 0
- .right = iWidth
- .top = 0
- .bottom = iHeight
- End With
- iDisplayTransformation = New ESRI.ArcGIS.Display.DisplayTransformation
- With iDisplayTransformation
- .VisibleBounds = iEnvelope
- .Bounds = iEnvelope
- .DeviceFrame = itagRECT
- .Resolution = iGraphics.DpiX
- End With
- iHDC = iGraphics.GetHdc.ToInt32
- '获取Geometry
- If TypeOf (iSymbol) Is ESRI.ArcGIS.Display.IMarkerSymbol Then
- Select Case iStyle
- Case 0
- iPoint = New ESRI.ArcGIS.Geometry.Point
- iPoint.PutCoords(iWidth / 2, iHeight / 2)
- iGeometry = iPoint
- End Select
- ElseIf TypeOf (iSymbol) Is ESRI.ArcGIS.Display.ILineSymbol Then
- iSegmentCollection = New ESRI.ArcGIS.Geometry.Path
- iPolyline = New ESRI.ArcGIS.Geometry.Polyline
- Select Case iStyle
- Case 0
- iSegmentCollection.AddSegment(CreateLine(0, iHeight / 2, iWidth, iHeight / 2))
- iPolyline.AddGeometry(iSegmentCollection)
- iGeometry = iPolyline
- Case 1
- iSegmentCollection.AddSegment(CreateLine(0, iHeight / 4, iWidth / 4, 3 * iHeight / 4))
- iSegmentCollection.AddSegment(CreateLine(iWidth / 4, 3 * iHeight / 4, 3 * iWidth / 4, iHeight / 4))
- iSegmentCollection.AddSegment(CreateLine(3 * iWidth / 4, iHeight / 4, iWidth, 3 * iHeight / 4))
- iPolyline.AddGeometry(iSegmentCollection)
- iGeometry = iPolyline
- End Select
- ElseIf TypeOf (iSymbol) Is ESRI.ArcGIS.Display.IFillSymbol Then
- iSegmentCollection = New ESRI.ArcGIS.Geometry.Ring
- iPolygon = New ESRI.ArcGIS.Geometry.Polygon
- Select Case iStyle
- Case 0
- iSegmentCollection.AddSegment(CreateLine(5, iHeight - 5, iWidth - 6, iHeight - 5))
- iSegmentCollection.AddSegment(CreateLine(iWidth - 6, iHeight - 5, iWidth - 6, 6))
- iSegmentCollection.AddSegment(CreateLine(iWidth - 6, 6, 5, 6))
- iRing = iSegmentCollection
- iRing.Close()
- iPolygon.AddGeometry(iSegmentCollection)
- iGeometry = iPolygon
- End Select
- ElseIf TypeOf (iSymbol) Is ESRI.ArcGIS.Display.ISimpleTextSymbol Then
- Select Case iStyle
- Case 0
- iPoint = New ESRI.ArcGIS.Geometry.Point
- iPoint.PutCoords(iWidth / 2, iHeight / 2)
- iGeometry = iPoint
- End Select
- End If
- '绘制图形
- iSymbol.SetupDC(iHDC, iDisplayTransformation)
- iSymbol.Draw(iGeometry)
- iSymbol.ResetDC()
- iGraphics.ReleaseHdc(iHDC)
- iGraphics.Dispose()
- SymbolToBitmap = iBitmap
- End Function
复制代码 过程基本就完成了，应该说没什么难度
|
