DrawingContext Classe

Definição

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

Herança

Object

DispatcherObject

DrawingContext

Implementações

IDisposable

Exemplos

O exemplo a seguir recupera um DrawingContext de um DrawingVisual e o usa para desenhar um retângulo.

// 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

O exemplo a seguir demonstra os PushOpacitycomandos , PushEffecte Pop . O DrawingContext é obtido de um DrawingGroup e exibido usando um Image controle .

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

Comentários

Use um DrawingContext para preencher um Visual ou um Drawing com conteúdo visual.

Embora os DrawingContext métodos de desenho pareçam semelhantes aos métodos de desenho do System.Drawing.Graphics tipo, eles funcionam de forma muito diferente: DrawingContext é usado com um sistema gráfico de modo retido, enquanto o System.Drawing.Graphics tipo é usado com um sistema gráfico de modo imediato. Ao usar os comandos de desenho de um DrawingContext objeto, na verdade, você está armazenando um conjunto de instruções de renderização (embora o mecanismo de armazenamento exato dependa do tipo de objeto que fornece o DrawingContext) que posteriormente será usado pelo sistema gráfico; você não está desenhando na tela em tempo real. Para obter mais informações sobre como funciona o sistema de gráficos do WPF (Windows Presentation Foundation), confira Visão geral da renderização de elementos gráficos do WPF.

Você nunca cria uma instância direta de um DrawingContext; você pode, no entanto, adquirir um contexto de desenho de determinados métodos, como DrawingGroup.Open e DrawingVisual.RenderOpen.

Propriedades

Métodos

Implantações explícitas de interface

Aplica-se a

Confira também

• DrawingGroup
• Drawing