DrawingContext Class

Reference

Definition

Namespace:: System.Windows.Media

Assembly:: PresentationCore.dll

Important

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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: Object

DispatcherObject
DrawingContext

Implements: IDisposable

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)	Draws an ellipse with the specified Brush and Pen.
DrawGeometry(Brush, Pen, Geometry)	Draws the specified Geometry using the specified Brush and Pen.
DrawGlyphRun(Brush, GlyphRun)	Draws the specified text.
DrawImage(ImageSource, Rect, AnimationClock)	Draws an image into the region defined by the specified Rect and applies the specified animation clock.
DrawImage(ImageSource, Rect)	Draws an image into the region defined by the specified Rect.
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, AnimationClock)	Draws a rectangle with the specified Brush and Pen and applies the specified animation clocks.
DrawRectangle(Brush, Pen, Rect)	Draws a rectangle with the specified Brush and Pen. The pen and the brush can be `null`.
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)	Draws a rounded rectangle with the specified Brush and Pen.
DrawText(FormattedText, Point)	Draws formatted text at the specified location.
DrawVideo(MediaPlayer, Rect, AnimationClock)	Draws a video into the specified region and applies the specified animation clock.
DrawVideo(MediaPlayer, Rect)	Draws a video into the specified region.
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, AnimationClock)	Pushes the specified opacity setting onto the drawing context and applies the specified animation clock.
PushOpacity(Double)	Pushes the specified opacity setting onto the drawing context.
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.

Applies to

Delen via