学步园

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