DrawingContext Class
Definition
Describes visual content using draw, push, and pop commands.
public ref class DrawingContext abstract : System::Windows::Threading::DispatcherObject, IDisposable
public abstract class DrawingContext : System.Windows.Threading.DispatcherObject, IDisposable
type DrawingContext = class
inherit DispatcherObject
interface IDisposable
Public MustInherit Class DrawingContext
Inherits DispatcherObject
Implements IDisposable
- Inheritance
- Implements
Examples
The following example retrieves a DrawingContext from a DrawingVisual and uses it to draw a rectangle.
// Create a DrawingVisual that contains a rectangle.
private DrawingVisual CreateDrawingVisualRectangle()
{
DrawingVisual drawingVisual = new DrawingVisual();
// Retrieve the DrawingContext in order to create new drawing content.
DrawingContext drawingContext = drawingVisual.RenderOpen();
// Create a rectangle and draw it in the DrawingContext.
Rect rect = new Rect(new System.Windows.Point(160, 100), new System.Windows.Size(320, 80));
drawingContext.DrawRectangle(System.Windows.Media.Brushes.LightBlue, (System.Windows.Media.Pen)null, rect);
// Persist the drawing content.
drawingContext.Close();
return drawingVisual;
}
' Create a DrawingVisual that contains a rectangle.
Private Function CreateDrawingVisualRectangle() As DrawingVisual
Dim drawingVisual As New DrawingVisual()
' Retrieve the DrawingContext in order to create new drawing content.
Dim drawingContext As DrawingContext = drawingVisual.RenderOpen()
' Create a rectangle and draw it in the DrawingContext.
Dim rect As New Rect(New Point(160, 100), New Size(320, 80))
drawingContext.DrawRectangle(Brushes.LightBlue, CType(Nothing, Pen), rect)
' Persist the drawing content.
drawingContext.Close()
Return drawingVisual
End Function
The next example demonstrates the PushOpacity, PushEffect, and Pop commands. The DrawingContext is obtained from a DrawingGroup and displayed using an Image control.
using System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Navigation;
using System.Windows.Media.Effects;
namespace SDKSample
{
public class PushEffectExample : Page
{
public PushEffectExample()
{
Pen shapeOutlinePen = new Pen(Brushes.Black, 2);
shapeOutlinePen.Freeze();
// Create a DrawingGroup
DrawingGroup dGroup = new DrawingGroup();
// Obtain a DrawingContext from
// the DrawingGroup.
using (DrawingContext dc = dGroup.Open())
{
// Draw a rectangle at full opacity.
dc.DrawRectangle(Brushes.Blue, shapeOutlinePen, new Rect(0, 0, 25, 25));
// Push an opacity change of 0.5.
// The opacity of each subsequent drawing will
// will be multiplied by 0.5.
dc.PushOpacity(0.5);
// This rectangle is drawn at 50% opacity.
dc.DrawRectangle(Brushes.Blue, shapeOutlinePen, new Rect(25, 25, 25, 25));
// Blurs subsquent drawings.
dc.PushEffect(new BlurBitmapEffect(), null);
// This rectangle is blurred and drawn at 50% opacity (0.5 x 0.5).
dc.DrawRectangle(Brushes.Blue, shapeOutlinePen, new Rect(50, 50, 25, 25));
// This rectangle is also blurred and drawn at 50% opacity.
dc.DrawRectangle(Brushes.Blue, shapeOutlinePen, new Rect(75, 75, 25, 25));
// Stop applying the blur to subsquent drawings.
dc.Pop();
// This rectangle is drawn at 50% opacity with no blur effect.
dc.DrawRectangle(Brushes.Blue, shapeOutlinePen, new Rect(100, 100, 25, 25));
}
// Display the drawing using an image control.
Image theImage = new Image();
DrawingImage dImageSource = new DrawingImage(dGroup);
theImage.Source = dImageSource;
this.Content = theImage;
}
}
}
Imports System.Windows.Media.Animation
Imports System.Windows.Media.Effects
Namespace SDKSample
Public Class PushEffectExample
Inherits Page
Public Sub New()
Dim shapeOutlinePen As New Pen(Brushes.Black, 2)
shapeOutlinePen.Freeze()
' Create a DrawingGroup
Dim dGroup As New DrawingGroup()
' Obtain a DrawingContext from
' the DrawingGroup.
Using dc As DrawingContext = dGroup.Open()
' Draw a rectangle at full opacity.
dc.DrawRectangle(Brushes.Blue, shapeOutlinePen, New Rect(0, 0, 25, 25))
' Push an opacity change of 0.5.
' The opacity of each subsequent drawing will
' will be multiplied by 0.5.
dc.PushOpacity(0.5)
' This rectangle is drawn at 50% opacity.
dc.DrawRectangle(Brushes.Blue, shapeOutlinePen, New Rect(25, 25, 25, 25))
' Blurs subsquent drawings.
dc.PushEffect(New BlurBitmapEffect(), Nothing)
' This rectangle is blurred and drawn at 50% opacity (0.5 x 0.5).
dc.DrawRectangle(Brushes.Blue, shapeOutlinePen, New Rect(50, 50, 25, 25))
' This rectangle is also blurred and drawn at 50% opacity.
dc.DrawRectangle(Brushes.Blue, shapeOutlinePen, New Rect(75, 75, 25, 25))
' Stop applying the blur to subsquent drawings.
dc.Pop()
' This rectangle is drawn at 50% opacity with no blur effect.
dc.DrawRectangle(Brushes.Blue, shapeOutlinePen, New Rect(100, 100, 25, 25))
End Using
' Display the drawing using an image control.
Dim theImage As New Image()
Dim dImageSource As New DrawingImage(dGroup)
theImage.Source = dImageSource
Me.Content = theImage
End Sub
End Class
End Namespace
Remarks
Use a DrawingContext to populate a Visual or a Drawing with visual content.
Although the DrawingContext draw methods appear similar to the draw methods of the System.Drawing.Graphics type, they function very differently: DrawingContext is used with a retained mode graphics system, while the System.Drawing.Graphics type is used with an immediate mode graphics system. When you use a DrawingContext object's draw commands, you are actually storing a set of rendering instructions (although the exact storage mechanism depends on the type of object that supplies the DrawingContext) that will later be used by the graphics system; you are not drawing to the screen in real-time. For more information about how the Windows Presentation Foundation (WPF) graphics system works, see WPF Graphics Rendering Overview.
You never directly instantiate a DrawingContext; you can, however, acquire a drawing context from certain methods, such as DrawingGroup.Open and DrawingVisual.RenderOpen.
Properties
Dispatcher |
Gets the Dispatcher this DispatcherObject is associated with. (Inherited from DispatcherObject) |
Methods
CheckAccess() |
Determines whether the calling thread has access to this DispatcherObject. (Inherited from DispatcherObject) |
Close() |
Closes the DrawingContext and flushes the content. Afterward, the DrawingContext cannot be modified. |
DisposeCore() |
Releases all resources used by the DrawingContext. |
DrawDrawing(Drawing) |
Draws the specified Drawing object. |
DrawEllipse(Brush, Pen, Point, AnimationClock, Double, AnimationClock, Double, AnimationClock) |
Draws an ellipse with the specified Brush and Pen and applies the specified animation clocks. |
DrawEllipse(Brush, Pen, Point, Double, Double) | |
DrawGeometry(Brush, Pen, Geometry) |
Draws the specified Geometry using the specified Brush and Pen. |
DrawGlyphRun(Brush, GlyphRun) |
Draws the specified text. |
DrawImage(ImageSource, Rect) |
Draws an image into the region defined by the specified Rect. |
DrawImage(ImageSource, Rect, AnimationClock) |
Draws an image into the region defined by the specified Rect and applies the specified animation clock. |
DrawLine(Pen, Point, AnimationClock, Point, AnimationClock) |
Draws a line between the specified points using the specified Pen and applies the specified animation clocks. |
DrawLine(Pen, Point, Point) |
Draws a line between the specified points using the specified Pen. |
DrawRectangle(Brush, Pen, Rect) |
Draws a rectangle with the specified Brush and Pen. The pen and the brush can be |
DrawRectangle(Brush, Pen, Rect, AnimationClock) |
Draws a rectangle with the specified Brush and Pen and applies the specified animation clocks. |
DrawRoundedRectangle(Brush, Pen, Rect, AnimationClock, Double, AnimationClock, Double, AnimationClock) |
Draws a rounded rectangle with the specified Brush and Pen and applies the specified animation clocks. |
DrawRoundedRectangle(Brush, Pen, Rect, Double, Double) | |
DrawText(FormattedText, Point) |
Draws formatted text at the specified location. |
DrawVideo(MediaPlayer, Rect) |
Draws a video into the specified region. |
DrawVideo(MediaPlayer, Rect, AnimationClock) |
Draws a video into the specified region and applies the specified animation clock. |
Equals(Object) |
Determines whether the specified object is equal to the current object. (Inherited from Object) |
GetHashCode() |
Serves as the default hash function. (Inherited from Object) |
GetType() |
Gets the Type of the current instance. (Inherited from Object) |
MemberwiseClone() |
Creates a shallow copy of the current Object. (Inherited from Object) |
Pop() |
Pops the last opacity mask, opacity, clip, effect, or transform operation that was pushed onto the drawing context. |
PushClip(Geometry) |
Pushes the specified clip region onto the drawing context. |
PushEffect(BitmapEffect, BitmapEffectInput) |
Obsolete.
Pushes the specified BitmapEffect onto the drawing context. |
PushGuidelineSet(GuidelineSet) |
Pushes the specified GuidelineSet onto the drawing context. |
PushOpacity(Double) |
Pushes the specified opacity setting onto the drawing context. |
PushOpacity(Double, AnimationClock) |
Pushes the specified opacity setting onto the drawing context and applies the specified animation clock. |
PushOpacityMask(Brush) |
Pushes the specified opacity mask onto the drawing context. |
PushTransform(Transform) |
Pushes the specified Transform onto the drawing context. |
ToString() |
Returns a string that represents the current object. (Inherited from Object) |
VerifyAccess() |
Enforces that the calling thread has access to this DispatcherObject. (Inherited from DispatcherObject) |
VerifyApiNonstructuralChange() |
This member supports the WPF infrastructure and is not intended to be used directly from your code. |
Explicit Interface Implementations
IDisposable.Dispose() |
This member supports the Windows Presentation Foundation (WPF) infrastructure and is not intended to be used directly from your code. |