给WPF示例图形加上方便查看大小的格子

有时，我们为了方便查看WPF图形的样式及比例等，需要一些辅助性的格线，置于图形、图像的背景中。

比如下图，就是为了更清晰地查看折线的图形，我们画了用于标示位置大小的背景格：

那么，怎么绘制这样的格子呢？

为了更通用些，我把它做成资源的形式，放到app.xaml文件中的 <Application.Resources>节内：
<Application
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    x:Class="Microsoft.Samples.Graphics.app"
    Startup="myAppStartingUp">
    <Application.Resources>
     
      <DrawingBrush x:Key="MyGridBrushResource" Viewport="0,0,10,10" ViewportUnits="Absolute" TileMode="Tile">
        <DrawingBrush.Drawing>
          <DrawingGroup>
            <DrawingGroup.Children>
              <GeometryDrawing Brush="White"><!-- 这里是格子填充颜色 -->
                <GeometryDrawing.Geometry>
                  <RectangleGeometry Rect="0,0,1,1" />
                </GeometryDrawing.Geometry>
              </GeometryDrawing>
              <GeometryDrawing Geometry="M0,0 L1,0 1,0.1, 0,0.1Z" Brush="#CCCCFF" /><!-- 这里是横线 -->
              <GeometryDrawing Geometry="M0,0 L0,1 0.1,1, 0.1,0Z" Brush="#CCCCFF" /><!-- 这里是竖线 -->
            </DrawingGroup.Children>
          </DrawingGroup>
        </DrawingBrush.Drawing>
      </DrawingBrush>  

      <!-- 这里是外框线 -->
      <Style x:Key="MyGridBorderStyle">
        <Setter Property="Border.Background" Value="{StaticResource MyGridBrushResource}"/>
        <Setter Property="Border.HorizontalAlignment" Value="Center"/>
        <Setter Property="Border.VerticalAlignment" Value="Top"/>
        <Setter Property="Border.BorderBrush" Value="Black"/>
        <Setter Property="Border.BorderThickness" Value="1"/>
      </Style>

    </Application.Resources>
</Application>

其中，Viewport="0,0,10,10"中的10,10表示格子的像素宽度、高度值。

使用方法：
// PolylineExample.xaml
<!-- This example shows how to draw Polyline elements. -->
<Page     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    x:Class="BrawDraw.Com.WPF.Graphics.PolylineExample"
    WindowTitle="Polyline Example">
<StackPanel>
  <StackPanel Margin="10">
    <Border Style="{StaticResource MyGridBorderStyle}">
      <Canvas Height="400" Width="400">
        <Polyline
          Points="10,110 60,10 110,110"
          Stroke="Black"
          StrokeThickness="4" />

        <Polyline
          Points="10,110 110,110 110,10"
          Stroke="Black"
          StrokeThickness="4"
          Canvas.Left="150" />

        </Canvas>
      </Border>
    </StackPanel>
  </StackPanel>
</Page>

C#代码：
// PolylineExample.xaml.cs
using System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Navigation;
using System.Windows.Shapes;
using System.Windows.Media;
using System.Windows.Media.Animation;

namespace BrawDraw.Com.WPF.Graphics
{
    public partial class PolylineExample : Page
    {
        public PolylineExample()
        {
            InitializeComponent();
        }
    }
}