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Shapes and basic drawing overview |
Enhance your user interface with ready-to-use shapes and several layers of rendering services in Windows Presentation Foundation (WPF). |
03/30/2017 |
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66d7a6d6-e3b6-47bc-8dfe-8a1b26f7d901 |
This topic gives an overview of how to draw with xref:System.Windows.Shapes.Shape objects. A xref:System.Windows.Shapes.Shape is a type of xref:System.Windows.UIElement that enables you to draw a shape to the screen. Because they are UI elements, xref:System.Windows.Shapes.Shape objects can be used inside xref:System.Windows.Controls.Panel elements and most controls.
Windows Presentation Foundation (WPF) offers several layers of access to graphics and rendering services. At the top layer, xref:System.Windows.Shapes.Shape objects are easy to use and provide many useful features, such as layout and participation in the Windows Presentation Foundation (WPF) event system.
Shape-related types are in the Windows.Shapes namespace. Geometry-related types are in the System.Windows.Media namespace.
WPF provides a number of ready-to-use xref:System.Windows.Shapes.Shape objects. All shape objects inherit from the xref:System.Windows.Shapes.Shape class. Available shape objects include xref:System.Windows.Shapes.Ellipse, xref:System.Windows.Shapes.Line, xref:System.Windows.Shapes.Path, xref:System.Windows.Shapes.Polygon, xref:System.Windows.Shapes.Polyline, and xref:System.Windows.Shapes.Rectangle. xref:System.Windows.Shapes.Shape objects share the following common properties.
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xref:System.Windows.Shapes.Shape.Stroke%2A: Describes how the shape's outline is painted.
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xref:System.Windows.Shapes.Shape.StrokeThickness%2A: Describes the thickness of the shape's outline.
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xref:System.Windows.Shapes.Shape.Fill%2A: Describes how the interior of the shape is painted.
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Data properties to specify coordinates and vertices, measured in device-independent pixels.
Because they derive from xref:System.Windows.UIElement, shape objects can be used inside panels and most controls. The xref:System.Windows.Controls.Canvas panel is a particularly good choice for creating complex drawings because it supports absolute positioning of its child objects.
The xref:System.Windows.Shapes.Line class enables you to draw a line between two points. The following example shows several ways to specify line coordinates and stroke properties.
[!code-xamldrawingwithshapeelements#LineExample1]
[!code-cppshapesprocedural#ShapesProceduralLine] [!code-csharpshapesprocedural#ShapesProceduralLine] [!code-vbshapesprocedural#ShapesProceduralLine]
The following image shows the rendered xref:System.Windows.Shapes.Line.
Although the xref:System.Windows.Shapes.Line class does provide a xref:System.Windows.Shapes.Shape.Fill%2A property, setting it has no effect because a xref:System.Windows.Shapes.Line has no area.
Another common shape is the xref:System.Windows.Shapes.Ellipse. Create an xref:System.Windows.Shapes.Ellipse by defining the shape's xref:System.Windows.FrameworkElement.Width%2A and xref:System.Windows.FrameworkElement.Height%2A properties. To draw a circle, specify an xref:System.Windows.Shapes.Ellipse whose xref:System.Windows.FrameworkElement.Width%2A and xref:System.Windows.FrameworkElement.Height%2A values are equal.
[!code-xamlShapeOverviews#ShapesOVW1]
[!code-csharpbrushesmiscsnippets_procedural_snip#SetBackgroundColorOfShapeCodeExampleWholePage] [!code-vbbrushesmiscsnippets_procedural_snip#SetBackgroundColorOfShapeCodeExampleWholePage]
The following image shows an example of a rendered xref:System.Windows.Shapes.Ellipse.
The xref:System.Windows.Shapes.Path class enables you to draw curves and complex shapes. These curves and shapes are described using xref:System.Windows.Media.Geometry objects. To use a xref:System.Windows.Shapes.Path, you create a xref:System.Windows.Media.Geometry and use it to set the xref:System.Windows.Shapes.Path object's xref:System.Windows.Shapes.Path.Data%2A property.
There are a variety of xref:System.Windows.Media.Geometry objects to choose from. The xref:System.Windows.Media.LineGeometry, xref:System.Windows.Media.RectangleGeometry, and xref:System.Windows.Media.EllipseGeometry classes describe relatively simple shapes. To create more complex shapes or create curves, use a xref:System.Windows.Media.PathGeometry.
xref:System.Windows.Media.PathGeometry objects are comprised of one or more xref:System.Windows.Media.PathFigure objects; each xref:System.Windows.Media.PathFigure represents a different "figure" or shape. Each xref:System.Windows.Media.PathFigure is itself comprised of one or more xref:System.Windows.Media.PathSegment objects, each representing a connected portion of the figure or shape. Segment types include the following: xref:System.Windows.Media.LineSegment, xref:System.Windows.Media.BezierSegment, and xref:System.Windows.Media.ArcSegment.
In the following example, a xref:System.Windows.Shapes.Path is used to draw a quadratic Bezier curve.
[!code-xamlgeometrysample#34]
The following image shows the rendered shape.
For more information about xref:System.Windows.Media.PathGeometry and the other xref:System.Windows.Media.Geometry classes, see the Geometry Overview.
In Extensible Application Markup Language (XAML), you may also use a special abbreviated syntax to describe a xref:System.Windows.Shapes.Path. In the following example, abbreviated syntax is used to draw a complex shape.
<Path Stroke="DarkGoldenRod" StrokeThickness="3"
Data="M 100,200 C 100,25 400,350 400,175 H 280" /> The following image shows a rendered xref:System.Windows.Shapes.Path.
The xref:System.Windows.Shapes.Path.Data%2A attribute string begins with the "moveto" command, indicated by M, which establishes a start point for the path in the coordinate system of the xref:System.Windows.Controls.Canvas. xref:System.Windows.Shapes.Path data parameters are case-sensitive. The capital M indicates an absolute location for the new current point. A lowercase m would indicate relative coordinates. The first segment is a cubic Bezier curve beginning at (100,200) and ending at (400,175), drawn using the two control points (100,25) and (400,350). This segment is indicated by the C command in the xref:System.Windows.Shapes.Path.Data%2A attribute string. Again, the capital C indicates an absolute path; the lowercase c would indicate a relative path.
The second segment begins with an absolute horizontal "lineto" command H, which specifies a line drawn from the preceding subpath's endpoint (400,175) to a new endpoint (280,175). Because it is a horizontal "lineto" command, the value specified is an x-coordinate.
For the complete path syntax, see the xref:System.Windows.Shapes.Path.Data%2A reference and Create a Shape by Using a PathGeometry.
xref:System.Windows.Media.Brush objects are used to paint a shape's xref:System.Windows.Shapes.Shape.Stroke%2A and xref:System.Windows.Shapes.Shape.Fill%2A. In the following example, the stroke and fill of an xref:System.Windows.Shapes.Ellipse are specified. Note that valid input for brush properties can be either a keyword or hexadecimal color value. For more information about available color keywords, see properties of the xref:System.Windows.Media.Colors class in the xref:System.Windows.Media namespace.
<Canvas Background="LightGray">
<Ellipse
Canvas.Top="50"
Canvas.Left="50"
Fill="#FFFFFF00"
Height="75"
Width="75"
StrokeThickness="5"
Stroke="#FF0000FF"/>
</Canvas> The following image shows the rendered xref:System.Windows.Shapes.Ellipse.
Alternatively, you can use property element syntax to explicitly create a xref:System.Windows.Media.SolidColorBrush object to paint the shape with a solid color.
<!-- This polygon shape uses pre-defined color values for its Stroke and
Fill properties.
The SolidColorBrush's Opacity property affects the fill color in
this case by making it slightly transparent (opacity of 0.4) so
that it blends with any underlying color. -->
<Polygon
Points="300,200 400,125 400,275 300,200"
Stroke="Purple"
StrokeThickness="2">
<Polygon.Fill>
<SolidColorBrush Color="Blue" Opacity="0.4"/>
</Polygon.Fill>
</Polygon> The following illustration shows the rendered shape.
You can also paint a shape's stroke or fill with gradients, images, patterns, and more. For more information, see the Painting with Solid Colors and Gradients Overview.
The xref:System.Windows.Shapes.Line, xref:System.Windows.Shapes.Path, xref:System.Windows.Shapes.Polygon, xref:System.Windows.Shapes.Polyline, and xref:System.Windows.Shapes.Rectangle classes all have a xref:System.Windows.Shapes.Shape.Stretch%2A property. This property determines how a xref:System.Windows.Shapes.Shape object's contents (the shape to be drawn) is stretched to fill the xref:System.Windows.Shapes.Shape object's layout space. A xref:System.Windows.Shapes.Shape object's layout space is the amount of space the xref:System.Windows.Shapes.Shape is allocated by the layout system, because of either an explicit xref:System.Windows.FrameworkElement.Width%2A and xref:System.Windows.FrameworkElement.Height%2A setting or because of its xref:System.Windows.FrameworkElement.HorizontalAlignment%2A and xref:System.Windows.FrameworkElement.VerticalAlignment%2A settings. For additional information on layout in Windows Presentation Foundation, see Layout overview.
The Stretch property takes one of the following values:
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xref:System.Windows.Media.Stretch.None: The xref:System.Windows.Shapes.Shape object's contents are not stretched.
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xref:System.Windows.Media.Stretch.Fill: The xref:System.Windows.Shapes.Shape object's contents are stretched to fill its layout space. Aspect ratio is not preserved.
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xref:System.Windows.Media.Stretch.Uniform: The xref:System.Windows.Shapes.Shape object's contents are stretched as much as possible to fill its layout space while preserving its original aspect ratio.
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xref:System.Windows.Media.Stretch.UniformToFill: The xref:System.Windows.Shapes.Shape object's contents are stretched to completely fill its layout space while preserving its original aspect ratio.
Note that, when a xref:System.Windows.Shapes.Shape object's contents are stretched, the xref:System.Windows.Shapes.Shape object's outline is painted after the stretching.
In the following example, a xref:System.Windows.Shapes.Polygon is used to draw a very small triangle from (0,0) to (0,1) to (1,1). The xref:System.Windows.Shapes.Polygon object's xref:System.Windows.FrameworkElement.Width%2A and xref:System.Windows.FrameworkElement.Height%2A are set to 100, and its stretch property is set to Fill. As a result, the xref:System.Windows.Shapes.Polygon object's contents (the triangle) are stretched to fill the larger space.
<Polygon
Points="0,0 0,1 1,1"
Fill="Blue"
Width="100"
Height="100"
Stretch="Fill"
Stroke="Black"
StrokeThickness="2" /> PointCollection myPointCollection = new PointCollection();
myPointCollection.Add(new Point(0,0));
myPointCollection.Add(new Point(0,1));
myPointCollection.Add(new Point(1,1));
Polygon myPolygon = new Polygon();
myPolygon.Points = myPointCollection;
myPolygon.Fill = Brushes.Blue;
myPolygon.Width = 100;
myPolygon.Height = 100;
myPolygon.Stretch = Stretch.Fill;
myPolygon.Stroke = Brushes.Black;
myPolygon.StrokeThickness = 2; The xref:System.Windows.Media.Transform class provides the means to transform shapes in a two-dimensional plane. The different types of transformation include rotation (xref:System.Windows.Media.RotateTransform), scale (xref:System.Windows.Media.ScaleTransform), skew (xref:System.Windows.Media.SkewTransform), and translation (xref:System.Windows.Media.TranslateTransform).
A common transform to apply to a shape is a rotation. To rotate a shape, create a xref:System.Windows.Media.RotateTransform and specify its xref:System.Windows.Media.RotateTransform.Angle%2A. An xref:System.Windows.Media.RotateTransform.Angle%2A of 45 rotates the element 45 degrees clockwise; an angle of 90 rotates the element 90 degrees clockwise; and so on. Set the xref:System.Windows.Media.RotateTransform.CenterX%2A and xref:System.Windows.Media.RotateTransform.CenterY%2A properties if you want to control the point about which the element is rotated. These property values are expressed in the coordinate space of the element being transformed. xref:System.Windows.Media.RotateTransform.CenterX%2A and xref:System.Windows.Media.RotateTransform.CenterY%2A have default values of zero. Finally, apply the xref:System.Windows.Media.RotateTransform to the element. If you don't want the transform to affect layout, set the shape's xref:System.Windows.UIElement.RenderTransform%2A property.
In the following example, a xref:System.Windows.Media.RotateTransform is used to rotate a shape 45 degrees about the shape's top left corner (0,0).
[!code-xamltransformssample#14]
In the next example, another shape is rotated 45 degrees, but this time it's rotated about the point (25,50).
[!code-xamltransformssample#15]
The following illustration shows the results of applying the two transforms.
In the previous examples, a single transform was applied to each shape object. To apply multiple transforms to a shape (or any other UI element), use a xref:System.Windows.Media.TransformGroup.