Share via

Как создать фигуру с помощью StreamGeometry

  • Статья

StreamGeometry является упрощенной альтернативой PathGeometry для создания геометрических фигур. Для описания сложной геометрии, если не нужна поддержка привязки данных, анимации или изменения, используйте StreamGeometry. Например, благодаря своей эффективности класс StreamGeometry хорошо подходит для описания графических элементов.

Создание треугольной модели StreamGeometry

В следующем примере используется синтаксис атрибутов для создания треугольного объекта StreamGeometry в 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>

Дополнительные сведения о синтаксисе атрибута StreamGeometry см. на странице Синтаксис разметки пути.

Использование StreamGeometry для определения треугольника

В следующем примере используется для StreamGeometry определения треугольника в коде. Сначала в примере мы создаем StreamGeometry, затем получаем StreamGeometryContext и используем его для описания треугольника.

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

Создание геометрической фигуры в коде

В следующем примере создается метод, который использует StreamGeometry и StreamGeometryContext для определения геометрической фигуры на основе указанных параметров.

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;
        }
    }
}


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

См. также