Painting with Images, Drawings, and Visuals

Painting with Images, Drawings, and...

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Microsoft Visual Studio 2008/.Net Framework 3.5

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Windows Presentation Foundation

Painting with Images, Drawings, and Visuals

This topic describes how to use ImageBrush, DrawingBrush, and VisualBrush objects to paint an area with an image, a Drawing, or a Visual.

This topic contains the following sections.

Prerequisites
Paint an Area with an Image
Example: Paint an Object with a Bitmap Image
Paint an Area with a Drawing
Example: Paint an Object with a Drawing
Paint an Area with a Visual
Example: Paint an Object with a Visual
Example: Create a Reflection
TileBrush Features
Related Topics

Prerequisites

To understand this topic, you should be familiar with the different types of brushes Windows Presentation Foundation (WPF) provides and their basic features. For an introduction, see the WPF Brushes Overview.

Paint an Area with an Image

An ImageBrush paints an area with an ImageSource. The most common type of ImageSource to use with an ImageBrush is a BitmapImage, which describes a bitmap graphic. You can use a DrawingImage to paint using a Drawing object, but it is simpler to use a DrawingBrush instead. For more information about ImageSource objects, see the Imaging Overview.

To paint with an ImageBrush, create a BitmapImage and use it to load the bitmap content. Then, use the BitmapImage to set the ImageSource property of the ImageBrush. Finally, apply the ImageBrush to the object you want to paint. In Extensible Application Markup Language (XAML), you can also just set the ImageSource property of the ImageBrush with the path of the image to load.

Like all Brush objects, an ImageBrush can be used to paint objects such as shapes, panels, controls, and text. The following illustration shows some effects that can be achieved with an ImageBrush.

Objects painted by an ImageBrush

By default, an ImageBrush stretches its image to completely fill the area being painted, possibly distorting the image if the painted area has a different aspect ratio than the image. You can change this behavior by changing the Stretch property from its default value of Fill to None, Uniform, or UniformToFill. Because ImageBrush is a type of TileBrush, you can specify exactly how an image brush fills the output area and even create patterns. For more information about advanced TileBrush features, see the TileBrush Overview.

Example: Paint an Object with a Bitmap Image

The following example uses an ImageBrush to paint the Background of a Canvas.

<Page
  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
  x:Class="Microsoft.Samples.BrushExamples.ImageBrushExample"
  WindowTitle="ImageBrush Example"
  Background="White">

  <StackPanel>

    <Canvas
      Height="200" Width="300">
      <Canvas.Background>
        <ImageBrush ImageSource="sampleImages\Waterlilies.jpg" />
      </Canvas.Background>
    </Canvas>


  </StackPanel>
</Page>

using System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Media;
using System.Windows.Media.Imaging;

namespace Microsoft.Samples.BrushExamples
{

    public class ImageBrushExample : Page
    {

        public ImageBrushExample()
        {

            StackPanel mainPanel = new StackPanel();
            canvasBackgroundExample(mainPanel);
            this.Content = mainPanel;

        }


        private void canvasBackgroundExample(Panel mainPanel)
        {

            BitmapImage theImage = new BitmapImage
                (new Uri("sampleImages\\Waterlilies.jpg", UriKind.Relative));

            ImageBrush myImageBrush = new ImageBrush(theImage);

            Canvas myCanvas = new Canvas();
            myCanvas.Width = 300;
            myCanvas.Height = 200;
            myCanvas.Background = myImageBrush;

            mainPanel.Children.Add(myCanvas);


        }

    }

}

Paint an Area with a Drawing

A DrawingBrush enables you to paint an area with shapes, text, images, and video. Shapes inside a drawing brush may themselves be painted with a solid color, gradient, image, or even another DrawingBrush. The following illustration demonstrates some uses of a DrawingBrush.

Objects painted by a DrawingBrush

A DrawingBrush paints an area with a Drawing object. A Drawing object describes visible content, such as a shape, bitmap, video, or a line of text. Different types of drawings describe different types of content. The following is a list of the different types of drawing objects.

GeometryDrawing – Draws a shape.
ImageDrawing – Draws an image.
GlyphRunDrawing – Draws text.
VideoDrawing – Plays an audio or video file.
DrawingGroup – Draws other drawings. Use a drawing group to combine other drawings into a single composite drawing.

For more information about Drawing objects, see the Drawing Objects Overview.

Like an ImageBrush, a DrawingBrush stretches its Drawing to fill its output area. You can override this behavior by changing the Stretch property from its default setting of Fill. For more information, see the Stretch property.

Example: Paint an Object with a Drawing

The following example shows how to paint an object with a drawing of three ellipses. A GeometryDrawing is used to describe the ellipses.

<Button Content="A Button">
  <Button.Background>
    <DrawingBrush>
      <DrawingBrush.Drawing>
        <GeometryDrawing Brush="LightBlue">
          <GeometryDrawing.Geometry>
            <GeometryGroup>
              <EllipseGeometry RadiusX="12.5" RadiusY="25" Center="25,50" />
              <EllipseGeometry RadiusX="12.5" RadiusY="25" Center="50,50" />
              <EllipseGeometry RadiusX="12.5" RadiusY="25" Center="75,50" />
            </GeometryGroup>
          </GeometryDrawing.Geometry>
          <GeometryDrawing.Pen>
            <Pen Thickness="1" Brush="Gray" />
          </GeometryDrawing.Pen>
        </GeometryDrawing>
      </DrawingBrush.Drawing>
    </DrawingBrush>
  </Button.Background>
</Button>

// Create a DrawingBrush.
DrawingBrush myDrawingBrush = new DrawingBrush();

// Create a drawing.
GeometryDrawing myGeometryDrawing = new GeometryDrawing();
myGeometryDrawing.Brush = Brushes.LightBlue;
myGeometryDrawing.Pen = new Pen(Brushes.Gray, 1);
GeometryGroup ellipses = new GeometryGroup();
ellipses.Children.Add(new EllipseGeometry(new Point(25,50), 12.5, 25));
ellipses.Children.Add(new EllipseGeometry(new Point(50,50), 12.5, 25));
ellipses.Children.Add(new EllipseGeometry(new Point(75,50), 12.5, 25));

myGeometryDrawing.Geometry = ellipses;
myDrawingBrush.Drawing = myGeometryDrawing;

Button myButton = new Button();
myButton.Content = "A Button";

// Use the DrawingBrush to paint the button's background.
myButton.Background = myDrawingBrush;

Paint an Area with a Visual

The most versatile and powerful of all the brushes, the VisualBrush paints an area with a Visual. A Visual is a low-level graphical type that serves as the ancestor of many useful graphical components. For example, the Window, FrameworkElement, and Control classes are all types of Visual objects. Using a VisualBrush, you can paint areas with almost any Windows Presentation Foundation (WPF) graphical object.

Note:
Although VisualBrush is a type of Freezable object, it cannot be frozen (made read-only) when its Visual property is set to a value other than null.

There are two ways to specify the Visual content of a VisualBrush.

Create a new Visual and use it to set the Visual property of the VisualBrush. For an example, see the Example: Paint an Object with a Visual section that follows.
Use an existing Visual, which creates a duplicate image of the target Visual. You can then use the VisualBrush to create interesting effects, such as reflection and magnification. For an example, see the Example: Create a Reflection section.

When you define a new Visual for a VisualBrush and that Visual is a UIElement (such as a panel or control), the layout system runs on the UIElement and its child elements when the AutoLayoutContent property is set to true. However, the root UIElement is essentially isolated from the rest of the system: styles, and external layout can't permeate this boundary. Therefore, you should explicitly specify the size of the root UIElement, because its only parent is the VisualBrush and therefore it cannot automatically size itself to the area being painted. For more information about layout in Windows Presentation Foundation (WPF), see the The Layout System.

Like ImageBrush and DrawingBrush, a VisualBrush stretches its content to fill its output area. You can override this behavior by changing the Stretch property from its default setting of Fill. For more information, see the Stretch property.

Example: Paint an Object with a Visual

In the following example, several controls and a panel are used to paint a rectangle.

<Rectangle Width="150" Height="150" Stroke="Black" Margin="5,0,5,0">
  <Rectangle.Fill>
    <VisualBrush>
      <VisualBrush.Visual>
        <StackPanel Background="White">
          <Rectangle Width="25" Height="25" Fill="Red" Margin="2" />
          <TextBlock FontSize="10pt" Margin="2">Hello, World!</TextBlock>
          <Button Margin="2">A Button</Button>
        </StackPanel>
      </VisualBrush.Visual>
    </VisualBrush>
  </Rectangle.Fill>
</Rectangle>

VisualBrush myVisualBrush = new VisualBrush();

// Create the visual brush's contents.
StackPanel myStackPanel = new StackPanel();
myStackPanel.Background = Brushes.White;

Rectangle redRectangle = new Rectangle();
redRectangle.Width = 25;
redRectangle.Height =25; 
redRectangle.Fill = Brushes.Red;
redRectangle.Margin = new Thickness(2);
myStackPanel.Children.Add(redRectangle);

TextBlock someText = new TextBlock();
FontSizeConverter myFontSizeConverter = new FontSizeConverter();
someText.FontSize = (double)myFontSizeConverter.ConvertFrom("10pt");
someText.Text = "Hello, World!";
someText.Margin = new Thickness(2);
myStackPanel.Children.Add(someText);

Button aButton = new Button();
aButton.Content = "A Button";
aButton.Margin = new Thickness(2);
myStackPanel.Children.Add(aButton);

// Use myStackPanel as myVisualBrush's content.
myVisualBrush.Visual = myStackPanel;

// Create a rectangle to paint.
Rectangle myRectangle = new Rectangle();
myRectangle.Width = 150;
myRectangle.Height = 150;
myRectangle.Stroke = Brushes.Black;
myRectangle.Margin = new Thickness(5,0,5,0);

// Use myVisualBrush to paint myRectangle.
myRectangle.Fill = myVisualBrush;

Example: Create a Reflection

The preceding example showed how to create a new Visual for use as a background. You can also use a VisualBrush to display an existing visual; this capability enables you to produce interesting visual effects, such as reflections and magnification. The following example uses a VisualBrush to create a reflection of a Border that contains several elements. The following illustration shows the output that this example produces.

A reflected Visual object

<Page  
  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
  Background="Black">


  <StackPanel Margin="50">

    <!-- The object to reflect. -->
    <Border Name="ReflectedVisual" Width="400">
      <Border.Background>
        <LinearGradientBrush StartPoint="0,0.5" EndPoint="1,0.5">
          <GradientStop Offset="0.0" Color="#CCCCFF" />
          <GradientStop Offset="1.0" Color="White" />
        </LinearGradientBrush>
      </Border.Background>
      <StackPanel Orientation="Horizontal" Margin="10">        
        <TextBlock TextWrapping="Wrap" Width="200" Margin="10">
          Lorem ipsum dolor sit amet, consectetuer adipiscing elit.
          Suspendisse vel ante. Donec luctus tortor sit amet est.
          Nullam pulvinar odio et wisi.
          Pellentesque quis magna. Sed pellentesque.
          Nulla euismod.
          Pellentesque habitant morbi tristique senectus et netus et malesuada fames ac turpis egestas.
        </TextBlock>
        <StackPanel>
          <Ellipse Margin="10" Height="50" Width="50" Fill="Black" />
          <Ellipse Margin="10" Height="50" Width="50" Fill="Black" />
          <Ellipse Margin="10" Height="50" Width="50" Fill="Black" />
        </StackPanel>
      </StackPanel>
    </Border>

    <Rectangle Height="1" Fill="Gray" HorizontalAlignment="Stretch" />

    <!-- The object to contain the reflection.-->
    <Rectangle 
      Height="{Binding Path=ActualHeight, ElementName=ReflectedVisual}" 
      Width="{Binding Path=ActualWidth, ElementName=ReflectedVisual}">
      <Rectangle.Fill>

        <!-- Creates the reflection. -->
        <VisualBrush 
          Opacity="0.75" Stretch="None"
          Visual="{Binding ElementName=ReflectedVisual}">
          <VisualBrush.RelativeTransform>

            <!-- Flip the reflection. -->
            <TransformGroup>
              <ScaleTransform ScaleX="1" ScaleY="-1" />
              <TranslateTransform  Y="1" />
            </TransformGroup>
          </VisualBrush.RelativeTransform>
        </VisualBrush>
      </Rectangle.Fill>

      <Rectangle.OpacityMask>
        <LinearGradientBrush StartPoint="0.5,0" EndPoint="0.5,1">
          <GradientStop Color="#FF000000" Offset="0.0" />
          <GradientStop Color="#33000000" Offset="0.5" />
          <GradientStop Color="#00000000" Offset="0.75" />
        </LinearGradientBrush>
      </Rectangle.OpacityMask>

      <Rectangle.BitmapEffect>
        <BlurBitmapEffect Radius="1.5" />
      </Rectangle.BitmapEffect>

    </Rectangle>
  </StackPanel>
</Page>

For additional examples that show how to magnify portions of the screen and how to create reflections, see the VisualBrush Sample.

TileBrush Features

ImageBrush, DrawingBrush, and VisualBrush are types of TileBrush objects. TileBrush objects provide you with a great deal of control over how an area is painted with an image, drawing, or visual. For example, instead of just painting an area with a single stretched image, you can paint an area with a series of image tiles that create a pattern.

A TileBrush has three primary components: content, tiles, and the output area.

Components of a TileBrush with a single tile

Components of a TileBrush with multiple tiles

For more information about the tiling features of TileBrush objects, see the TileBrush Overview.

Tasks

Concepts

Reference