Silverlight缩略图生成(使用WriteableBitmap类)

前段時間，一直因為silverlight生成縮略圖而飽受困擾。

雖然聽說過WriteableBitmap這個類，能生成縮略圖。也曾百度上面粗略看過，一直沒找到合適的生成縮略圖的辦法。

今天，再次試過，終于成功。下面貼出代碼，實際的向大家說明一下，縮略圖是如何生成的。

/// <summary>
		/// 生成縮略圖
		/// </summary>
		/// <param name="bitmap">要轉換的位圖</param>
		/// <returns>返回WriteableBitmap</returns>
		public WriteableBitmap RenderThumbnail(BitmapImage bitmap)
		{
			Image img = new Image();
			img.Width = 150;
			img.Height = 150;
			img.source = bitmap;
			WriteableBitmap Wimg = new WriteableBitmap(img,null);
			Wimg.Invalidate();
			return Wimg;
		}

下面展示一個示例：

<UserControl x:Class="SilverlightTest.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="300" d:DesignWidth="400">


    <Grid x:Name="LayoutRoot" Background="White">
        <Grid.RowDeFinitions>
            <RowDeFinition></RowDeFinition>
            <RowDeFinition></RowDeFinition>
        </Grid.RowDeFinitions>
        <Image x:Name="TestImg1" Grid.Row="0" Source="/SilverlightTest;component/Images/20120229_reg_page1_09.jpg" Stretch="None"></Image>
        <Image x:Name="TestImg"  Grid.Row="1" Source="/SilverlightTest;component/Images/20120229_reg_page1_09.jpg" Stretch="None"></Image>
        <TextBlock x:Name="txt" Grid.Row="1" VerticalAlignment="Bottom" HorizontalAlignment="Center"></TextBlock>
    </Grid>
</UserControl>

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;
using System.Windows.Media.Imaging;

namespace SilverlightTest
{
	public partial class MainPage : UserControl
	{
		public MainPage()
		{
			InitializeComponent();
			BitmapImage bmap = TestImg.source as BitmapImage;
			WriteableBitmap wimg = this.RenderThumbnail(bmap);
			TestImg.source = wimg;
			txt.Text ="原圖大小為：" +bmap.PixelWidth + "Px;縮略圖寬度為：" + wimg.PixelWidth+"Px";

		}
		/// <summary>
		/// 生成縮略圖
		/// </summary>
		/// <param name="bitmap">要轉換的位圖</param>
		/// <returns>返回WriteableBitmap</returns>
		public WriteableBitmap RenderThumbnail(BitmapImage bitmap)
		{
			Image img = new Image();
			img.Width = 150;
			img.Height = 150;
			img.source = bitmap;
			WriteableBitmap Wimg = new WriteableBitmap(img,null);
			Wimg.Invalidate();
			return Wimg;
		}
	}
}

請看如下效果：

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