Silverlight 引路蜂二维图形库示例：概述

Windows Phone 7 并不是Windows Mobile 6.x 的升级版，也就是说 Windows Phone 7 SDK 没有提供对 Windows Mobile .Net Compact Version的向下兼容。“它所带来的后果之一就是，之前的Windows Moible应用程序无法在Windows Phone 7系列上运行。” Windows Phone 7 SDK 是基于Silverlight。因此一些原先定义在.Net Compact Framework中的包和类在 Window Phone 7 SDK 中没有对应的类。比如System.Drawing , System.Drawing.Image 。在Windows Phone 7 SDK 提供类似功能的是System.Windows.Shapes和System.Windows.Media.Imaging 。当如果想动态生成二维图形或是图像，Silverlight和 GDI+ 相比不是特别方便。

引路蜂开发包中提供了一个平台无关的高效二维图形库，提供了诸如LineCap, LineJoin, Brush, TextBrush, Path 等类。它的画板为一个二维数组（内部采用一维数组），每个数组元素为一个32位整数，代表ARGB颜色值。SilverlightSystem.Windows.Media.Imaging 中定义了WriteableBitmap Class ，WriteableBitmap的Pixels属性也是一个整数数组，其定义方法和引路蜂开发包中定义的一致。因此通过WriteableBitmap作为桥梁，就可以把引路蜂开发包Graphics2D绘制的图形图像显示到Silverlight的XAML 的Image 元素中。

下图显示了Silverlight 引路蜂二维图形开发包中定义的包和类。

最后以一个简单的例子说明一下图形包的用法。也可以参见Windows Mobile引路蜂地图开发示例：二维图形库。

创建一个Silverlight项目，修改MainPage.xml ，如下所示。

<UserControl x:Class=”SilverlightGraphics2DDemo.MainPage”
xmlns=”http://schemas.microsoft.com/winfx/2006/xaml/presentation”
xmlns:x=”http://schemas.microsoft.com/winfx/2006/xaml”
xmlns:d=”http://schemas.microsoft.com/expression/blend/2008”
xmlns:mc=”http://schemas.openxmlformats.org/markup-compatibility/2006”
mc:Ignorable=”d”
d:DesignHeight=”640″ d:DesignWidth=”480″>

<Grid x:Name=”LayoutRoot” Width=”480″ Height=”640″>
<StackPanel>
<TextBlock HorizontalAlignment=”Center”
FontSize=”14″ Text=”Silverlight Graphics 2D Demo” />
<Border Width=”480″ Height=”640″ Background=”Black”>
<Image x:Name=”image” Width=”480″ Height=”640″/>
</Border>
</StackPanel>
</Grid>
< /UserControl>

XAML中定义了一个Image对象用于显示图像显示的结果。

修改MainPage.xaml.cs

using System;using System.Windows.Controls;using System.Windows.Media.Imaging;using Mapdigit.Drawing;using Mapdigit.Drawing.Geometry;using Color = Mapdigit.Drawing.Color;namespace SilverlightGraphics2DDemo{    public partial class MainPage : UserControl    {        private Graphics2D graphics2D;        private int screenWidth = 480;        private int screenHeight = 640;         WriteableBitmap bmp;        public MainPage()        {            InitializeComponent();            graphics2D = new Graphics2D(screenWidth, screenHeight);            Ellipse circle, oval, leaf, stem;            Area circ, ov, leaf1, leaf2, st1, st2;            circle = new Ellipse();            oval = new Ellipse();            leaf = new Ellipse();            stem = new Ellipse();            circ = new Area(circle);            ov = new Area(oval);            leaf1 = new Area(leaf);            leaf2 = new Area(leaf);            st1 = new Area(stem);            st2 = new Area(stem);            graphics2D.Reset();            graphics2D.Clear(Color.White);            int w = screenWidth;            int h = screenHeight;            int ew = w / 2;            int eh = h / 2;            SolidBrush brush = new SolidBrush(Color.Green);            graphics2D.DefaultBrush = brush;            // Creates the first leaf by filling the intersection of two Area            //objects created from an ellipse.            leaf.SetFrame(ew - 16, eh - 29, 15, 15);            leaf1 = new Area(leaf);            leaf.SetFrame(ew - 14, eh - 47, 30, 30);            leaf2 = new Area(leaf);            leaf1.Intersect(leaf2);            graphics2D.Fill(null, leaf1);             // Creates the second leaf.            leaf.SetFrame(ew + 1, eh - 29, 15, 15);            leaf1 = new Area(leaf);            leaf2.Intersect(leaf1);            graphics2D.Fill(null, leaf2);             brush = new SolidBrush(Color.Black);            graphics2D.DefaultBrush = brush;             // Creates the stem by filling the Area resulting from the            //subtraction of two Area objects created from an ellipse.            stem.SetFrame(ew, eh - 42, 40, 40);            st1 = new Area(stem);            stem.SetFrame(ew + 3, eh - 47, 50, 50);            st2 = new Area(stem);            st1.Subtract(st2);            graphics2D.Fill(null, st1);             brush = new SolidBrush(Color.Yellow);            graphics2D.DefaultBrush = brush;             // Creates the pear itself by filling the Area resulting from the            //union of two Area objects created by two different ellipses.            circle.SetFrame(ew - 25, eh, 50, 50);            oval.SetFrame(ew - 19, eh - 20, 40, 70);            circ = new Area(circle);            ov = new Area(oval);            circ.Add(ov);            graphics2D.Fill(null, circ);             bmp = new WriteableBitmap(screenWidth, screenHeight);            image.Source = bmp;            RefreshBitmap();        }        private void RefreshBitmap()        {            Buffer.BlockCopy(graphics2D.Argb, 0, bmp.Pixels, 0, bmp.Pixels.Length * 4);        }     }}

Buffer.BlockCopy(graphics2D.Argb, 0, bmp.Pixels, 0, bmp.Pixels.Length * 4);就是将Graphics2D内部int32数组拷贝到WriteableBitmap的Pixels中。上面代码通过多个几何图形拼成一个梨子如下图所示：

Graphics2D 示例