如何在Windows Phone中压缩图片并保存
文章信息
本文介绍了怎样降低图片的分辨率并将其保存到图片库。
介绍
将图片上传到服务器，但有时图片太大，为了节省流量需要对图片进行压缩后上传。我们可以利用PictureDecoder.DecodeJpeg(Stream, Int32, Int32)方法来返回一个 WriteableBitmap 类型的新图片。 下面介绍具体的实现步骤。
首先，我们使用以下代码添加按钮和图片控件到用户界面上。
<Grid x:Name="ContentPanel" Grid.Row="1" Margin="12,0,12,0">
<Image x:Name="img" Height="300" VerticalAlignment="Top" />
<Button Content="加载图片" Height="82" HorizontalAlignment="Left" Margin="150,0,0,219" Name="button1" VerticalAlignment="Bottom" Width="160" Click="button1_Click" />
<Button Content="保存图片" Height="72" HorizontalAlignment="Left" Margin="150,376,0,0" Name="button2" VerticalAlignment="Top" Width="160" Click="button2_Click" />
<Button Content="查看图片" Height="72" HorizontalAlignment="Left" Margin="150,438,0,0" Name="button3" VerticalAlignment="Top" Width="160" Click="button3_Click" />
<TextBox Height="72" HorizontalAlignment="Left" Margin="105,535,0,0" Name="textBox1" Text="80" VerticalAlignment="Top" Width="114" />
<TextBox Height="72" HorizontalAlignment="Left" Margin="225,535,0,0" Name="textBox2" Text="80" VerticalAlignment="Top" Width="116" />
<TextBlock Height="46" HorizontalAlignment="Left" Margin="12,555,0,0" Name="textBlock1" Text="设置目标分辨率" VerticalAlignment="Top" Width="90" />
</Grid>
下面，我们需要为项目添加必要的命名空间Microsoft.Xna.Framework，鼠标右击Reference，找到该命名空间点击添加。打开MainPage.xaml.cs，添加以下指令。
using Microsoft.Phone.Tasks;
using System.Windows.Media.Imaging;
using System.Windows.Resources;
using Microsoft.Phone;
using System.IO.IsolatedStorage;
using System.IO;
using Microsoft.Xna.Framework.Media;
在按钮点击事件中我们将项目夹中的图片加载到用户界面上，注意记得将目标图片的Build Action设为Content。
private void button1_Click(object sender, RoutedEventArgs e)
{
//为JPEG文件创建一个流
StreamResourceInfo sri = null;
//将Tulips.jpg的Build Action设为Content
Uri jpegUri = new Uri("Images/Tulips.jpg", UriKind.Relative);
sri = Application.GetResourceStream(jpegUri);
//将该流解码
WriteableBitmap bitmap = PictureDecoder.DecodeJpeg(sri.Stream);
img.Source = bitmap;
}
接下来，获取用户界面上所输入的目标分辨率值并为按钮点击事件添加button2_Click中的代码，将转换过的图片保存到图片库中。
int newPixelWidth;
int newPixelHeight;
public MainPage()
{
InitializeComponent();
//从页面读取输入值作为目标分辨率
newPixelWidth = int.Parse(textBox1.Text.ToString());
newPixelHeight = int.Parse(textBox2.Text.ToString());
textBox1.TextChanged += new TextChangedEventHandler(textBox1_TextChanged);
textBox2.TextChanged += new TextChangedEventHandler(textBox2_TextChanged);
}
void textBox2_TextChanged(object sender, TextChangedEventArgs e)
{
//textBox不为空
if (textBox2.Text != "" && int.Parse(textBox2.Text.ToString()) != 0)
{
newPixelHeight = int.Parse(textBox2.Text.ToString());
}
}
void textBox1_TextChanged(object sender, TextChangedEventArgs e)
{
if (textBox1.Text != "" && int.Parse(textBox1.Text.ToString()) != 0)
{
newPixelWidth = int.Parse(textBox1.Text.ToString());
}
}
private void button2_Click(object sender, RoutedEventArgs e)
{
String tempjpg = "tempimg";
//创建虚拟存储
var myStore = IsolatedStorageFile.GetUserStoreForApplication();
if (myStore.FileExists(tempjpg))
{
myStore.DeleteFile(tempjpg);
}
IsolatedStorageFileStream myFileStream = myStore.CreateFile(tempjpg);
StreamResourceInfo sri = null;
sri = Application.GetResourceStream(new Uri("Images/Tulips.jpg", UriKind.Relative));
//创建WriteableBitmap对象
BitmapImage bitmap = new BitmapImage();
bitmap.CreateOptions = BitmapCreateOptions.None;
bitmap.SetSource(sri.Stream);
WriteableBitmap wb = new WriteableBitmap(bitmap);
//WriteableBitmap对象编码，设置目标分辨率
wb.SaveJpeg(myFileStream, newPixelWidth, newPixelHeight, 0, 85);
myFileStream.Close();
myFileStream = myStore.OpenFile(tempjpg, FileMode.Open, FileAccess.Read);
//保存图片到图片库
MediaLibrary library = new MediaLibrary();
Picture pic = library.SavePicture("SavedPicture.jpg", myFileStream);
myFileStream.Close();
}
最后，利用照片选择器PhotoChooserTask打开图片库，查看我们所保存的图片。
//实例化选择器
PhotoChooserTask photoChooserTask = new PhotoChooserTask();
BitmapImage bimg;
private void button3_Click(object sender, RoutedEventArgs e)
{
//打开图片库
photoChooserTask.Show();
photoChooserTask.Completed += new EventHandler<PhotoResult>(photoChooserTask_Completed);
}
void photoChooserTask_Completed(object sender, PhotoResult e)
{
if (e.TaskResult == TaskResult.OK)
{
bimg = new BitmapImage();
bimg.SetSource(e.ChosenPhoto);
//设置Image控件的数据源
img.Source = bimg;
}
}
项目调试
选择“调试|启动调试”菜单命令运行应用程序。下面是项目截图。
下载
源代码：* File:ImageCompress.zip
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