blocks|key|900207|text|一个非常基本的示例。我确信有优化的空间，你可以从它做一个单独的类，可以处理大量的请求，但至少它是工作的，你可以根据你的需要来塑造它。还要注意的是，每次我们报告进度时，此示例都会创建一个图像，您应该避免它！每隔5%25左右制作一张图片，以避免较大的开销。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|900208|Xaml：|900209|<Window+x:Class="ScrollViewerTest.MainWindow"
++++xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
++++xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
++++Title="MainWindow"+Height="350"+Width="525"
++++DataContext="{Binding+RelativeSource={RelativeSource+Self}}">
++<StackPanel>
++++<TextBlock+Text="{Binding+Path=Progress,+StringFormat=Progress:+{0}}"+/>
++++<Image+Source="{Binding+Path=Image}"+/>
++</StackPanel>
</Window>|code-block|syntax|javascript|900210|代码隐藏：|900211|public+partial+class+MainWindow+:+Window,+INotifyPropertyChanged
{

++#region+Public+Properties

++private+int+_progress;
++public+int+Progress
++{
++++get+{+return+_progress;+}
++++set
++++{
++++++if+(_progress+!=+value)
++++++{
++++++++_progress+=+value;

++++++++if+(PropertyChanged+!=+null)
++++++++++PropertyChanged(this,+new+PropertyChangedEventArgs("Progress"));
++++++}
++++}
++}

++private+BitmapImage+image;
++public+BitmapImage+Image
++{
++++get+{+return+image;+}
++++set
++++{
++++++if+(image+!=+value)
++++++{
++++++++image+=+value;
++++++++if+(PropertyChanged+!=+null)
++++++++++PropertyChanged(this,+new+PropertyChangedEventArgs("Image"));
++++++}
++++}
++}

++#endregion

++BackgroundWorker+worker+=+new+BackgroundWorker();

++public+MainWindow()
++{
++++InitializeComponent();

++++worker.DoWork+%2B=+backgroundWorker1_DoWork;
++++worker.ProgressChanged+%2B=+new+ProgressChangedEventHandler(worker_ProgressChanged);
++++worker.WorkerReportsProgress+=+true;
++++worker.RunWorkerAsync(@"http://Tools.CentralShooters.co.nz/Images/ProgressiveSample1.jpg");
++}

++//+This+function+is+based+on+code+from
++//+++http://devtoolshed.com/content/c-download-file-progress-bar
++private+void+backgroundWorker1_DoWork(object+sender,+DoWorkEventArgs+e)
++{
++++//+the+URL+to+download+the+file+from
++++string+sUrlToReadFileFrom+=+e.Argument+as+string;

++++//+first,+we+need+to+get+the+exact+size+(in+bytes)+of+the+file+we+are+downloading
++++Uri+url+=+new+Uri(sUrlToReadFileFrom);
++++System.Net.HttpWebRequest+request+=+(System.Net.HttpWebRequest)System.Net.WebRequest.Create(url);
++++System.Net.HttpWebResponse+response+=+(System.Net.HttpWebResponse)request.GetResponse();
++++response.Close();
++++//+gets+the+size+of+the+file+in+bytes
++++Int64+iSize+=+response.ContentLength;

++++//+keeps+track+of+the+total+bytes+downloaded+so+we+can+update+the+progress+bar
++++Int64+iRunningByteTotal+=+0;

++++//+use+the+webclient+object+to+download+the+file
++++using+(System.Net.WebClient+client+=+new+System.Net.WebClient())
++++{
++++++//+open+the+file+at+the+remote+URL+for+reading
++++++using+(System.IO.Stream+streamRemote+=+client.OpenRead(new+Uri(sUrlToReadFileFrom)))
++++++{
++++++++using+(Stream+streamLocal+=+new+MemoryStream((int)iSize))
++++++++{
++++++++++//+loop+the+stream+and+get+the+file+into+the+byte+buffer
++++++++++int+iByteSize+=+0;
++++++++++byte[]+byteBuffer+=+new+byte[iSize];
++++++++++while+((iByteSize+=+streamRemote.Read(byteBuffer,+0,+byteBuffer.Length))+>+0)
++++++++++{
++++++++++++//+write+the+bytes+to+the+file+system+at+the+file+path+specified
++++++++++++streamLocal.Write(byteBuffer,+0,+iByteSize);
++++++++++++iRunningByteTotal+%2B=+iByteSize;

++++++++++++//+calculate+the+progress+out+of+a+base+"100"
++++++++++++double+dIndex+=+(double)(iRunningByteTotal);
++++++++++++double+dTotal+=+(double)byteBuffer.Length;
++++++++++++double+dProgressPercentage+=+(dIndex+/+dTotal);
++++++++++++int+iProgressPercentage+=+(int)(dProgressPercentage+*+100);

++++++++++++//+update+the+progress+bar,+and+we+pass+our+MemoryStream,+
++++++++++++//++so+we+can+use+it+in+the+progress+changed+event+handler
++++++++++++worker.ReportProgress(iProgressPercentage,+streamLocal);
++++++++++}

++++++++++//+clean+up+the+file+stream
++++++++++streamLocal.Close();
++++++++}

++++++++//+close+the+connection+to+the+remote+server
++++++++streamRemote.Close();
++++++}
++++}
++}

++void+worker_ProgressChanged(object+sender,+ProgressChangedEventArgs+e)
++{
++++Dispatcher.BeginInvoke(
+++++++++System.Windows.Threading.DispatcherPriority.Normal,
+++++++++new+Action(delegate()
+++++++++{
+++++++++++MemoryStream+stream+=+e.UserState+as+MemoryStream;

+++++++++++BitmapImage+bi+=+new+BitmapImage();
+++++++++++bi.BeginInit();
+++++++++++bi.StreamSource+=+new+MemoryStream(stream.ToArray());
+++++++++++bi.EndInit();

+++++++++++this.Progress+=+e.ProgressPercentage;
+++++++++++this.Image+=+bi;
+++++++++}
+++++++));
++}

++public+event+PropertyChangedEventHandler+PropertyChanged;
}|900212|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|P|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|Q|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|R|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|S|8|@]|9|@]|A|$G|H]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

A very basic sample. Im sure there are room for optimizations, and you can do a separate class from it that can handle numerous request, but at least its working, and you can shape it for your needs. Also note that this sample creates an image every time that we report a progress, you should avoid it! Do an image about every 5% or so to avoid a big overhead.

Xaml: 

<pre><code>&lt;Window x:Class="ScrollViewerTest.MainWindow"
 xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
 xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
 Title="MainWindow" Height="350" Width="525"
 DataContext="{Binding RelativeSource={RelativeSource Self}}"&gt;
 &lt;StackPanel&gt;
 &lt;TextBlock Text="{Binding Path=Progress, StringFormat=Progress: {0}}" /&gt;
 &lt;Image Source="{Binding Path=Image}" /&gt;
 &lt;/StackPanel&gt;
&lt;/Window&gt;
</code></pre>

Code-behind: 



<pre class="lang-cs prettyprint-override"><code>public partial class MainWindow : Window, INotifyPropertyChanged
{

 #region Public Properties

 private int _progress;
 public int Progress
 {
 get { return _progress; }
 set
 {
 if (_progress != value)
 {
 _progress = value;

 if (PropertyChanged != null)
 PropertyChanged(this, new PropertyChangedEventArgs("Progress"));
 }
 }
 }

 private BitmapImage image;
 public BitmapImage Image
 {
 get { return image; }
 set
 {
 if (image != value)
 {
 image = value;
 if (PropertyChanged != null)
 PropertyChanged(this, new PropertyChangedEventArgs("Image"));
 }
 }
 }

 #endregion

 BackgroundWorker worker = new BackgroundWorker();

 public MainWindow()
 {
 InitializeComponent();

 worker.DoWork += backgroundWorker1_DoWork;
 worker.ProgressChanged += new ProgressChangedEventHandler(worker_ProgressChanged);
 worker.WorkerReportsProgress = true;
 worker.RunWorkerAsync(@"http://Tools.CentralShooters.co.nz/Images/ProgressiveSample1.jpg");
 }

 // This function is based on code from
 // http://devtoolshed.com/content/c-download-file-progress-bar
 private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
 {
 // the URL to download the file from
 string sUrlToReadFileFrom = e.Argument as string;

 // first, we need to get the exact size (in bytes) of the file we are downloading
 Uri url = new Uri(sUrlToReadFileFrom);
 System.Net.HttpWebRequest request = (System.Net.HttpWebRequest)System.Net.WebRequest.Create(url);
 System.Net.HttpWebResponse response = (System.Net.HttpWebResponse)request.GetResponse();
 response.Close();
 // gets the size of the file in bytes
 Int64 iSize = response.ContentLength;

 // keeps track of the total bytes downloaded so we can update the progress bar
 Int64 iRunningByteTotal = 0;

 // use the webclient object to download the file
 using (System.Net.WebClient client = new System.Net.WebClient())
 {
 // open the file at the remote URL for reading
 using (System.IO.Stream streamRemote = client.OpenRead(new Uri(sUrlToReadFileFrom)))
 {
 using (Stream streamLocal = new MemoryStream((int)iSize))
 {
 // loop the stream and get the file into the byte buffer
 int iByteSize = 0;
 byte[] byteBuffer = new byte[iSize];
 while ((iByteSize = streamRemote.Read(byteBuffer, 0, byteBuffer.Length)) &gt; 0)
 {
 // write the bytes to the file system at the file path specified
 streamLocal.Write(byteBuffer, 0, iByteSize);
 iRunningByteTotal += iByteSize;

 // calculate the progress out of a base "100"
 double dIndex = (double)(iRunningByteTotal);
 double dTotal = (double)byteBuffer.Length;
 double dProgressPercentage = (dIndex / dTotal);
 int iProgressPercentage = (int)(dProgressPercentage * 100);

 // update the progress bar, and we pass our MemoryStream, 
 // so we can use it in the progress changed event handler
 worker.ReportProgress(iProgressPercentage, streamLocal);
 }

 // clean up the file stream
 streamLocal.Close();
 }

 // close the connection to the remote server
 streamRemote.Close();
 }
 }
 }

 void worker_ProgressChanged(object sender, ProgressChangedEventArgs e)
 {
 Dispatcher.BeginInvoke(
 System.Windows.Threading.DispatcherPriority.Normal,
 new Action(delegate()
 {
 MemoryStream stream = e.UserState as MemoryStream;

 BitmapImage bi = new BitmapImage();
 bi.BeginInit();
 bi.StreamSource = new MemoryStream(stream.ToArray());
 bi.EndInit();

 this.Progress = e.ProgressPercentage;
 this.Image = bi;
 }
 ));
 }

 public event PropertyChangedEventHandler PropertyChanged;
}
</code></pre>

blocks|key|900255|text|这似乎是Image控件的一个缺点。也许你可以创建一个从图像继承的StreamImage，在构造函数中获取一个流，从流中读取后台的字节，计算出它是否足够了，用到目前为止读取的字节构造一个内部“模糊图像”，然后迭代地呈现这个图像，直到它拥有所有的字节。您必须理解渐进式JPEG的字节是如何发送的--我想这并不简单。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|900256|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

This does seem to be a shortcoming of the Image control. Maybe you could create a StreamImage that inherits from Image, takes a stream in the constructor, reads bytes in the background from the stream, figures out when it has enough, constructs an internal "fuzzy image" with the bytes read so far and renders that iteratively until it has all the bytes. You'd have to understand how bytes of a progressive JPEG are sent--I don't imagine it is simple.

How to display a progressive JPEG as it loads from a web URL? I am trying to display a Google Maps image in a image control in WPF, but I want to keep the advantage of the image being a progressive JPG.

How to load a progressive JPG in WPF?

<pre><code>Image imgMap;
BitmapImage mapLoader = new BitmapImage();

mapLoader.BeginInit();
mapLoader.UriSource = new Uri(URL);
mapLoader.EndInit();

imgMap.Source = mapLoader;
</code></pre>

Currently, I make do with this. It will only shows the image after it loads completely. I want to show it progressively.

How can I display a Progressive JPEG in WPF?

Windows

如何显示从web URL加载的渐进式JPEG？我试图在WPF的图像控件中显示一个谷歌地图图像，但我想保持图像是一个渐进式JPG的优势。如何在WPF中加载渐进式JPG？Image imgMap;BitmapImage mapLoader = new BitmapImage();mapLoader.BeginInit();...

问如何在WPF中显示渐进式JPEG？
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