How to: Use Clipping with a Region

One of the properties of the Graphics class is the clip region. All drawing done by a given Graphics object is restricted to the clip region of that Graphics object. You can set the clip region by calling the SetClip method.

Example

The following example constructs a path that consists of a single polygon. Then the code constructs a region, based on that path. The region is passed to the SetClip method of a Graphics object, and then two strings are drawn.

The following illustration shows the clipped strings:

👁 Screenshot that shows clipped strings.

 // 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));

' 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))

Compiling the Code

The preceding example is designed for use with Windows Forms, and it requires PaintEventArgs e, which is a parameter of PaintEventHandler.

See also

• Regions in GDI+
• Using Regions