Como: Create a Shape Using a StreamGeometry
StreamGeometry is light-weight alternative to PathGeometry for creating geometric shapes. Use a StreamGeometry when you need to describe a complex geometry but do not want the overhead of supporting data binding, animation, or modification. For example, because of its efficiency, the StreamGeometry class is a good choice for describing adorners.
Exemplo
The following example uses attribute syntax to create a triangular StreamGeometry in XAML.
<Page xmlns="https://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="https://schemas.microsoft.com/winfx/2006/xaml">
<StackPanel>
<Path Data="F0 M10,100 L100,100 100,50Z"
StrokeThickness="1" Stroke="Black"/>
</StackPanel>
</Page>
For more information about StreamGeometry attribute syntax, see the Sintaxe de Marcação de Caminho page.
The next example uses a StreamGeometry to define a triangle in code. First, the example creates a StreamGeometry, then obtains a StreamGeometryContext and uses it to describe the triangle.
Imports System
Imports System.Windows
Imports System.Windows.Controls
Imports System.Windows.Media
Imports System.Windows.Shapes
Namespace SDKSample
' Use StreamGeometry with StreamGeometryContext to define a triangle shape.
Partial Public Class StreamGeometryTriangleExample
Inherits Page
Public Sub New()
' Create a path to draw a geometry with.
Dim myPath As New Path()
myPath.Stroke = Brushes.Black
myPath.StrokeThickness = 1
' Create a StreamGeometry to use to specify myPath.
Dim geometry As New StreamGeometry()
geometry.FillRule = FillRule.EvenOdd
' Open a StreamGeometryContext that can be used to describe this StreamGeometry
' object's contents.
Using ctx As StreamGeometryContext = geometry.Open()
' Begin the triangle at the point specified. Notice that the shape is set to
' be closed so only two lines need to be specified below to make the triangle.
ctx.BeginFigure(New Point(10, 100), True, True) ' is closed - is filled
' Draw a line to the next specified point.
ctx.LineTo(New Point(100, 100), True, False) ' is smooth join - is stroked
' Draw another line to the next specified point.
ctx.LineTo(New Point(100, 50), True, False) ' is smooth join - is stroked
End Using
' Freeze the geometry (make it unmodifiable)
' for additional performance benefits.
geometry.Freeze()
' Specify the shape (triangle) of the Path using the StreamGeometry.
myPath.Data = geometry
' Add path shape to the UI.
Dim mainPanel As New StackPanel()
mainPanel.Children.Add(myPath)
Me.Content = mainPanel
End Sub
End Class
End Namespace
using System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Media;
using System.Windows.Shapes;
namespace SDKSample
{
// Use StreamGeometry with StreamGeometryContext to define a triangle shape.
public partial class StreamGeometryTriangleExample : Page
{
public StreamGeometryTriangleExample()
{
// Create a path to draw a geometry with.
Path myPath = new Path();
myPath.Stroke = Brushes.Black;
myPath.StrokeThickness = 1;
// Create a StreamGeometry to use to specify myPath.
StreamGeometry geometry = new StreamGeometry();
geometry.FillRule = FillRule.EvenOdd;
// Open a StreamGeometryContext that can be used to describe this StreamGeometry
// object's contents.
using (StreamGeometryContext ctx = geometry.Open())
{
// Begin the triangle at the point specified. Notice that the shape is set to
// be closed so only two lines need to be specified below to make the triangle.
ctx.BeginFigure(new Point(10, 100), true /* is filled */, true /* is closed */);
// Draw a line to the next specified point.
ctx.LineTo(new Point(100, 100), true /* is stroked */, false /* is smooth join */);
// Draw another line to the next specified point.
ctx.LineTo(new Point(100, 50), true /* is stroked */, false /* is smooth join */);
}
// Freeze the geometry (make it unmodifiable)
// for additional performance benefits.
geometry.Freeze();
// Specify the shape (triangle) of the Path using the StreamGeometry.
myPath.Data = geometry;
// Add path shape to the UI.
StackPanel mainPanel = new StackPanel();
mainPanel.Children.Add(myPath);
this.Content = mainPanel;
}
}
}
O próximo exemplo cria um método que usa um StreamGeometry e StreamGeometryContext para definir uma forma geométrica, com base nos parâmetros especificados.
Imports System
Imports System.Windows
Imports System.Windows.Controls
Imports System.Windows.Media
Imports System.Windows.Shapes
Namespace SDKSample
Partial Public Class StreamGeometryExample
Inherits Page
Public Sub New()
' Create a path to draw a geometry with.
Dim myPath As New Path()
myPath.Stroke = Brushes.Black
myPath.StrokeThickness = 1
' Create a StreamGeometry to use to specify myPath.
Dim theGeometry As StreamGeometry = BuildRegularPolygon(New Point(200, 200), 200, 8, 0)
theGeometry.FillRule = FillRule.EvenOdd
' Freeze the geometry (make it unmodifiable)
' for additional performance benefits.
theGeometry.Freeze()
' Use the StreamGeometry returned by the BuildRegularPolygon to
' specify the shape of the path.
myPath.Data = theGeometry
' Add path shape to the UI.
Dim mainPanel As New StackPanel()
mainPanel.Children.Add(myPath)
Me.Content = mainPanel
End Sub
Private Function BuildRegularPolygon(ByVal c As Point, ByVal r As Double, ByVal numSides As Integer, ByVal offsetDegree As Double) As StreamGeometry
' c is the center, r is the radius,
' numSides the number of sides, offsetDegree the offset in Degrees.
' Do not add the last point.
Dim geometry As New StreamGeometry()
Using ctx As StreamGeometryContext = geometry.Open()
ctx.BeginFigure(New Point(), True, True) ' is closed - is filled
Dim [step] As Double = 2 * Math.PI / Math.Max(numSides, 3)
Dim cur As Point = c
Dim a As Double = Math.PI * offsetDegree / 180.0
Dim i As Integer = 0
Do While i < numSides
cur.X = c.X + r * Math.Cos(a)
cur.Y = c.Y + r * Math.Sin(a)
ctx.LineTo(cur, True, False) ' is smooth join - is stroked
i += 1
a += [step]
Loop
End Using
Return geometry
End Function
End Class
End Namespace
using System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Media;
using System.Windows.Shapes;
namespace SDKSample
{
public partial class StreamGeometryExample : Page
{
public StreamGeometryExample()
{
// Create a path to draw a geometry with.
Path myPath = new Path();
myPath.Stroke = Brushes.Black;
myPath.StrokeThickness = 1;
// Create a StreamGeometry to use to specify myPath.
StreamGeometry theGeometry = BuildRegularPolygon(new Point(200, 200), 200, 8, 0);
theGeometry.FillRule = FillRule.EvenOdd;
// Freeze the geometry (make it unmodifiable)
// for additional performance benefits.
theGeometry.Freeze();
// Use the StreamGeometry returned by the BuildRegularPolygon to
// specify the shape of the path.
myPath.Data = theGeometry;
// Add path shape to the UI.
StackPanel mainPanel = new StackPanel();
mainPanel.Children.Add(myPath);
this.Content = mainPanel;
}
StreamGeometry BuildRegularPolygon(Point c, double r, int numSides, double offsetDegree)
{
// c is the center, r is the radius,
// numSides the number of sides, offsetDegree the offset in Degrees.
// Do not add the last point.
StreamGeometry geometry = new StreamGeometry();
using (StreamGeometryContext ctx = geometry.Open())
{
ctx.BeginFigure(new Point(), true /* is filled */, true /* is closed */);
double step = 2 * Math.PI / Math.Max(numSides, 3);
Point cur = c;
double a = Math.PI * offsetDegree / 180.0;
for (int i = 0; i < numSides; i++, a += step)
{
cur.X = c.X + r * Math.Cos(a);
cur.Y = c.Y + r * Math.Sin(a);
ctx.LineTo(cur, true /* is stroked */, false /* is smooth join */);
}
}
return geometry;
}
}
}
Consulte também
Tarefas
Como: Criar um Shape usando um PathGeometry