Drawing Brush
The Drawing object in WPF represents a 2-D drawing that
include shapes, text, video, image and other drawings. A Drawing Brush
represented by the DrawingBrush object paints a surface with a drawing. The
DrawingGroup, GeometryDrawing, GlyphRunDrawing, ImageDrawing, and VideoDrawing
classes are inherited from the Drawing class. That means we can create any of
these objects to be painted by a DrawingBrush.
Creating a Drawing Brush
The DrawingBrush element in XAML creates a drawing brush.
The following code snippet creates a drawing brush and sets
the Drawing property. The Drawing property can be an element inherited from the
Drawing such as a GeometryDrawing.
<DrawingBrush >
<DrawingBrush.Drawing />
</DrawingBrush>
We can fill a shape with a drawing brush by setting a
shape's Fill property to the image brush. The code snippet in Listing 23
creates a rectangle shape sets the Fill property to a DrawingBrush.
<Grid Name="LayoutRoot">
<Rectangle Width="200" Height="200" Stroke="Black" StrokeThickness="0">
<Rectangle.Fill>
<DrawingBrush >
<DrawingBrush.Drawing>
<GeometryDrawing Brush="Yellow">
<GeometryDrawing.Geometry>
<GeometryGroup>
<RectangleGeometry Rect="50,25,25,25" />
<RectangleGeometry Rect="25,50,25,25" />
</GeometryGroup>
</GeometryDrawing.Geometry>
<GeometryDrawing.Pen>
<Pen Thickness="5">
<Pen.Brush>
<LinearGradientBrush>
<GradientStop Offset="0.0" Color="Blue" />
<GradientStop Offset="1.0" Color="Black" />
</LinearGradientBrush>
</Pen.Brush>
</Pen>
</GeometryDrawing.Pen>
</GeometryDrawing>
</DrawingBrush.Drawing>
</DrawingBrush>
</Rectangle.Fill>
</Rectangle>
</Grid>
Listing 23
The output looks like Figure 27.
Figure 27. A shape filled with a Drawing brush
The Viewport property determines the size and position of
the base tile when the TileMode of a DrawingBrush is not set to None, and the ViewportUnits
property determines whether the Viewport is specified using absolute or
relative coordinates. If the coordinates are relative, they are relative to the
size of the output area. The point (0,0) represents the top left corner of the
output area, and (1,1) represents the bottom right corner of the output area.
To specify that the Viewport property uses absolute coordinates, set the ViewportUnits
property to Absolute.
The TileMode property of DrawingBrush represents the tile
mode that is a type if a TileMode enumeration. The TileMode enumeration has
Tile, FlipX, FlipY, FlipXY, and None values.
The following code snippet sets the Viewport and TileMode
properties of a DrawingBrush.
<DrawingBrush
Viewport="0,0,0.25, 0.25" TileMode="Tile">
Figure 28, 29, and 30 show the tile modes values Tile,
FilpXY, and FlipX.
Figure 28. A shape filled with a Drawing
brush in Tile mode
Figure 29. A shape filled with a Drawing
brush with TileMode as FlipXY
Figure 30. A shape filled with a Drawing
brush with TileMode as FlipX
One of the key examples of tile mode is create a chess board
like image that has a repeating rectangle with black and white background
colors. The CreateARectangleWithDrawingBrush method
listed in Listing 24 draws a chess board like rectangle with a drawing brush dynamically.
private void CreateARectangleWithDrawingBrush()
{
// Create a
background recntangle
Rectangle
chessBoard = new Rectangle();
chessBoard.Width = 300;
chessBoard.Height = 300;
// Create a
DrawingBrush
DrawingBrush
blackBrush = new DrawingBrush();
// Create a
Geometry with white background
GeometryDrawing
backgroundSquare =
new GeometryDrawing(
Brushes.White,
null,
new
RectangleGeometry(new
Rect(0, 0, 400, 400)));
// Create a
GeometryGroup that will be added to Geometry
GeometryGroup
gGroup = new GeometryGroup();
gGroup.Children.Add(new RectangleGeometry(new Rect(0, 0, 200, 200)));
gGroup.Children.Add(new RectangleGeometry(new Rect(200, 200, 200, 200)));
// Create a
GeomertyDrawing
GeometryDrawing
checkers = new GeometryDrawing(new SolidColorBrush(Colors.Black), null,
gGroup);
DrawingGroup
checkersDrawingGroup = new DrawingGroup();
checkersDrawingGroup.Children.Add(backgroundSquare);
checkersDrawingGroup.Children.Add(checkers);
blackBrush.Drawing = checkersDrawingGroup;
// Set Viewport
and TimeMode
blackBrush.Viewport = new Rect(0, 0, 0.25, 0.25);
blackBrush.TileMode = TileMode.Tile;
// Fill rectangle
with a DrawingBrush
chessBoard.Fill = blackBrush;
LayoutRoot.Children.Add(chessBoard);
}
Listing 24
The output of Listing 24 looks like Figure 31.
Figure 31. A chess board