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Handleiding: Een vorm creëren met StreamGeometry

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StreamGeometry is een lichtgewicht alternatief voor PathGeometry voor het maken van geometrische vormen. Gebruik een StreamGeometry wanneer u een complexe geometrie moet beschrijven, maar niet de overhead van ondersteunende gegevensbinding, animatie of wijziging wilt. Vanwege zijn efficiëntie is de StreamGeometry-klasse bijvoorbeeld een goede keuze voor het beschrijven van versierders.

Een driehoekige StreamGeometry maken

In het volgende voorbeeld wordt de syntaxis van kenmerken gebruikt om een driehoekige StreamGeometry te maken in XAML.

<Page xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
  <StackPanel>
  
    <Path Data="F0 M10,100 L100,100 100,50Z" 
      StrokeThickness="1" Stroke="Black"/>

  </StackPanel>
</Page>

Raadpleeg de pagina Path-opmaaksyntaxis voor meer informatie over de syntaxis van het StreamGeometry-kenmerk.

Een StreamGeometry gebruiken om een driehoek te definiëren

In het volgende voorbeeld wordt een StreamGeometry gebruikt om een driehoek in code te definiëren. Eerst wordt in het voorbeeld een StreamGeometrygemaakt en wordt vervolgens een StreamGeometryContext verkregen en gebruikt om de driehoek te beschrijven.

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;
        }
    }
}


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

Een geometrische vorm maken in code

In het volgende voorbeeld wordt een methode gemaakt die gebruikmaakt van een StreamGeometry en StreamGeometryContext om een geometrische vorm te definiëren op basis van opgegeven parameters.

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())
            {
                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);
                    if (i == 0)
                        ctx.BeginFigure(cur, true /* is filled */, true /* is closed */);
                    else
                        ctx.LineTo(cur, true /* is stroked */, false /* is smooth join */);
                }
            }

            return geometry;
        }
    }
}


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()

                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

                For i = 0 To numSides - 1
                    cur.X = c.X + r * Math.Cos(a)
                    cur.Y = c.Y + r * Math.Sin(a)
                    If i = 0 Then
                        ctx.BeginFigure(cur, True, True) ' is closed  -  is filled 
                    Else
                        ctx.LineTo(cur, True, False) ' is smooth join  -  is stroked 
                    End If
                    a += [step]
                Next

            End Using

            Return geometry
        End Function
    End Class
End Namespace

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