Windows 窗体组件 > 产品 > XtraGrid > 概念 > 外观定制 > Alpha 混合和背景图像 > 使用自定义绘制实现 Alpha 混合

使用 Alpha 混合技术，可以增强控件的外观。这包括把背景图像指派到网格，并使用透明画笔和画刷绘制视图元素。请参阅 Alpha 混合概述主题获得关于此项技术的细节，以及实现方式的一个列表。本主题描述如何通过自定义绘制实现 Alpha 混合。

自定义绘制和 Alpha 混合

自定义绘制视图脚注 —— 示例

下面的示例代码接管了 GridView.CustomDrawFooter 事件，来自定义绘制视图的脚注。它使用透明画刷填充脚注的背景，然后绘制“The XtraGrid Suite”字符串。下面的插图展示了运行结果 (假设已经为网格指派了一幅背景图像)。

C#	复制代码
using DevExpress.XtraGrid.Views.Base; private void gridView1_CustomDrawFooter(object sender, RowObjectCustomDrawEventArgs e) { Color colorLeft = Color.FromArgb(150, Color.Gold); Color colorCenter = Color.FromArgb(100, Color.Blue); Color colorRight = Color.FromArgb(100, Color.Green); Rectangle leftRect = new Rectangle(e.Bounds.X, e.Bounds.Y, e.Bounds.Width / 2, e.Bounds.Height); Rectangle rightRect = new Rectangle(e.Bounds.X + e.Bounds.Width / 2, e.Bounds.Y, e.Bounds.Width / 2, e.Bounds.Height); // Fills the footer's background. using(LinearGradientBrush leftBrush = new LinearGradientBrush(leftRect, colorLeft, colorCenter, LinearGradientMode.Horizontal), rightBrush = new LinearGradientBrush(rightRect, colorCenter, colorRight, LinearGradientMode.Horizontal)) { e.Graphics.FillRectangle(leftBrush, leftRect); e.Graphics.FillRectangle(rightBrush, rightRect); } // Draws the border. ControlPaint.DrawBorder3D(e.Graphics, e.Bounds, Border3DStyle.Raised); StringFormat sf = new StringFormat(); sf.LineAlignment = StringAlignment.Center; sf.Alignment = StringAlignment.Near; sf.Trimming = StringTrimming.EllipsisCharacter; Font font = new Font("Tahoma", 8, FontStyle.Bold); // Draws the text. e.Graphics.DrawString("The XtraGrid Suite", font, new SolidBrush(Color.Navy), e.Bounds, sf); // Prohibit default painting. e.Handled = true; }

复制代码

using DevExpress.XtraGrid.Views.Base;

private void gridView1_CustomDrawFooter(object sender, RowObjectCustomDrawEventArgs e) {
   Color colorLeft = Color.FromArgb(150, Color.Gold);
   Color colorCenter = Color.FromArgb(100, Color.Blue);
   Color colorRight = Color.FromArgb(100, Color.Green);
   Rectangle leftRect = new Rectangle(e.Bounds.X, e.Bounds.Y, 
     e.Bounds.Width / 2, e.Bounds.Height);
   Rectangle rightRect = new Rectangle(e.Bounds.X + e.Bounds.Width / 2, 
     e.Bounds.Y, e.Bounds.Width / 2, e.Bounds.Height);
   // Fills the footer's background.
   using(LinearGradientBrush leftBrush = new LinearGradientBrush(leftRect, colorLeft, colorCenter, 
     LinearGradientMode.Horizontal),
            rightBrush = new LinearGradientBrush(rightRect, colorCenter, colorRight, 
              LinearGradientMode.Horizontal)) {
      e.Graphics.FillRectangle(leftBrush, leftRect);
      e.Graphics.FillRectangle(rightBrush, rightRect);
   }
   // Draws the border.
   ControlPaint.DrawBorder3D(e.Graphics, e.Bounds, Border3DStyle.Raised);
   
   StringFormat sf = new StringFormat();
   sf.LineAlignment = StringAlignment.Center;
   sf.Alignment = StringAlignment.Near;
   sf.Trimming = StringTrimming.EllipsisCharacter;
   Font font = new Font("Tahoma", 8, FontStyle.Bold);
   // Draws the text.
   e.Graphics.DrawString("The XtraGrid Suite", font, new SolidBrush(Color.Navy), e.Bounds, sf);
   // Prohibit default painting.
   e.Handled = true;
}

Visual Basic	复制代码
Imports DevExpress.XtraGrid.Views.Base Private Sub GridView1_CustomDrawFooter(ByVal sender As Object, _ ByVal e As DevExpress.XtraGrid.Views.Base.RowObjectCustomDrawEventArgs) _ Handles GridView1.CustomDrawFooter Dim ColorLeft As Color = Color.FromArgb(150, Color.Gold) Dim ColorCenter As Color = Color.FromArgb(100, Color.Blue) Dim ColorRight As Color = Color.FromArgb(100, Color.Green) Dim LeftRect As Rectangle = New Rectangle(e.Bounds.X, e.Bounds.Y, _ e.Bounds.Width / 2, e.Bounds.Height) Dim RightRect As Rectangle = New Rectangle(e.Bounds.X + e.Bounds.Width / 2, _ e.Bounds.Y, e.Bounds.Width / 2, e.Bounds.Height) Dim LeftBrush As LinearGradientBrush = New LinearGradientBrush(LeftRect, ColorLeft, _ ColorCenter, LinearGradientMode.Horizontal) Dim RightBrush As LinearGradientBrush = New LinearGradientBrush(RightRect, _ ColorCenter, ColorRight, LinearGradientMode.Horizontal) ' Fills the footer's background. e.Graphics.FillRectangle(LeftBrush, LeftRect) e.Graphics.FillRectangle(RightBrush, RightRect) LeftBrush.Dispose() RightBrush.Dispose() ' Draws the border. ControlPaint.DrawBorder3D(e.Graphics, e.Bounds, Border3DStyle.Raised) Dim Sf As StringFormat = New StringFormat Sf.LineAlignment = StringAlignment.Center Sf.Alignment = StringAlignment.Near Sf.Trimming = StringTrimming.EllipsisCharacter Dim font As Font = New Font("Tahoma", 8, FontStyle.Bold) ' Draws the text. e.Graphics.DrawString("The XtraGrid Suite", font, New SolidBrush(Color.Navy), _ e.Bounds.X, e.Bounds.Y, Sf) ' Prohibit default painting. e.Handled = True End Sub

Visual Basic

复制代码

Imports DevExpress.XtraGrid.Views.Base

Private Sub GridView1_CustomDrawFooter(ByVal sender As Object, _
ByVal e As DevExpress.XtraGrid.Views.Base.RowObjectCustomDrawEventArgs) _
Handles GridView1.CustomDrawFooter
   Dim ColorLeft As Color = Color.FromArgb(150, Color.Gold)
   Dim ColorCenter As Color = Color.FromArgb(100, Color.Blue)
   Dim ColorRight As Color = Color.FromArgb(100, Color.Green)
   Dim LeftRect As Rectangle = New Rectangle(e.Bounds.X, e.Bounds.Y, _
     e.Bounds.Width / 2, e.Bounds.Height)
   Dim RightRect As Rectangle = New Rectangle(e.Bounds.X + e.Bounds.Width / 2, _
     e.Bounds.Y, e.Bounds.Width / 2, e.Bounds.Height)
   Dim LeftBrush As LinearGradientBrush = New LinearGradientBrush(LeftRect, ColorLeft, _
     ColorCenter, LinearGradientMode.Horizontal)
   Dim RightBrush As LinearGradientBrush = New LinearGradientBrush(RightRect, _
     ColorCenter, ColorRight, LinearGradientMode.Horizontal)
   ' Fills the footer's background.
   e.Graphics.FillRectangle(LeftBrush, LeftRect)
   e.Graphics.FillRectangle(RightBrush, RightRect)
   LeftBrush.Dispose()
   RightBrush.Dispose()
   ' Draws the border.
   ControlPaint.DrawBorder3D(e.Graphics, e.Bounds, Border3DStyle.Raised)

   Dim Sf As StringFormat = New StringFormat
   Sf.LineAlignment = StringAlignment.Center
   Sf.Alignment = StringAlignment.Near
   Sf.Trimming = StringTrimming.EllipsisCharacter
   Dim font As Font = New Font("Tahoma", 8, FontStyle.Bold)
   ' Draws the text.
   e.Graphics.DrawString("The XtraGrid Suite", font, New SolidBrush(Color.Navy), _
     e.Bounds.X, e.Bounds.Y, Sf)
   ' Prohibit default painting.
   e.Handled = True
End Sub