如何：对区域使用剪辑
更新：2007 年 11 月
Graphics 类的一个属性是剪辑区域。所有由给定的 Graphics 对象进行的绘制都限制在 Graphics 对象的剪辑区域中。可通过调用 SetClip 方法设置剪辑区域。
示例
下面的示例构造由一个多边形组成的路径。然后，该代码根据该路径构造一个区域。将该区域传递给 Graphics 对象的 SetClip 方法，然后绘制两个字符串。
下面的插图显示这个经剪辑的字符串。
.png)
' Create a path that consists of a single polygon.
Dim polyPoints As Point() = { _
New Point(10, 10), _
New Point(150, 10), _
New Point(100, 75), _
New Point(100, 150)}
Dim path As New GraphicsPath()
path.AddPolygon(polyPoints)
' Construct a region based on the path.
Dim [region] As New [Region](path)
' Draw the outline of the region.
Dim pen As Pen = Pens.Black
e.Graphics.DrawPath(pen, path)
' Set the clipping region of the Graphics object.
e.Graphics.SetClip([region], CombineMode.Replace)
' Draw some clipped strings.
Dim fontFamily As New FontFamily("Arial")
Dim font As New Font( _
fontFamily, _
36, _
FontStyle.Bold, _
GraphicsUnit.Pixel)
Dim solidBrush As New SolidBrush(Color.FromArgb(255, 255, 0, 0))
e.Graphics.DrawString( _
"A Clipping Region", _
font, _
solidBrush, _
New PointF(15, 25))
e.Graphics.DrawString( _
"A Clipping Region", _
font, _
solidBrush, _
New PointF(15, 68))
// Create a path that consists of a single polygon.
Point[] polyPoints = {
new Point(10, 10),
new Point(150, 10),
new Point(100, 75),
new Point(100, 150)};
GraphicsPath path = new GraphicsPath();
path.AddPolygon(polyPoints);
// Construct a region based on the path.
Region region = new Region(path);
// Draw the outline of the region.
Pen pen = Pens.Black;
e.Graphics.DrawPath(pen, path);
// Set the clipping region of the Graphics object.
e.Graphics.SetClip(region, CombineMode.Replace);
// Draw some clipped strings.
FontFamily fontFamily = new FontFamily("Arial");
Font font = new Font(
fontFamily,
36, FontStyle.Bold,
GraphicsUnit.Pixel);
SolidBrush solidBrush = new SolidBrush(Color.FromArgb(255, 255, 0, 0));
e.Graphics.DrawString(
"A Clipping Region",
font, solidBrush,
new PointF(15, 25));
e.Graphics.DrawString(
"A Clipping Region",
font,
solidBrush,
new PointF(15, 68));
编译代码
前面的示例是为使用 Windows 窗体而设计的，它需要 PaintEventHandler 的参数 PaintEventArgse。