Public Sub StartFeedGetInformation( _
   ByVal totalPages As Boolean, _
   ByVal pageNumber As Integer _
) 

Visual Basic (Usage)	Copy Code
Dim instance As RasterCodecs Dim totalPages As Boolean Dim pageNumber As Integer   instance.StartFeedGetInformation(totalPages, pageNumber)

public void StartFeedGetInformation( 
   bool totalPages,
   int pageNumber
)

public:
void StartFeedGetInformation( 
   bool totalPages,
   int pageNumber
) 

Parameters

totalPages

true to query the file for total number of pages, false otherwise.

pageNumber

1-based index to the page number to query.

This example will use feed information to get information of an image from a url

Visual Basic

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Public Sub FeedGetInformationExample()    RasterCodecs.Startup()    Dim codecs As New RasterCodecs()    Dim url As String = "http://www.leadtools.com/images/web-header.jpg"    ' Create a WebRequest for the URL    Dim request As WebRequest = WebRequest.Create(url)    request.Proxy.Credentials = CredentialCache.DefaultCredentials    ' reduce the timeout to 20 sec    request.Timeout = 20000    Dim response As WebResponse = request.GetResponse()    Try       Dim strm As Stream = response.GetResponseStream()       ' Read chunks from the stream and feed load to the image       codecs.StartFeedGetInformation(True, 1)       Const bufferSize As Integer = 1024       Dim buffer(bufferSize - 1) As Byte       Dim more As Boolean       Do          Application.DoEvents()          Dim read As Integer = strm.Read(buffer, 0, bufferSize)          Console.WriteLine("Downloading {0} bytes", read)          If (read > 0) Then             more = codecs.FeedGetInformation(buffer, 0, read)          Else             ' no more image data in the stream             more = False          End If       Loop While more    Finally       response.Close()    End Try    Dim info As CodecsImageInfo = codecs.StopFeedGetInformation()    ' Clean up    codecs.Dispose()    RasterCodecs.Shutdown()    ' Show the information    MessageBox.Show(info.ToString()) End Sub

C#

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public void FeedGetInformationExample()  {     RasterCodecs.Startup();     RasterCodecs codecs = new RasterCodecs();       string url = @"http://www.leadtools.com/images/web-header.jpg";       // Create a WebRequest for the URL     WebRequest request = WebRequest.Create(url);     request.Proxy.Credentials = CredentialCache.DefaultCredentials;       // reduce the timeout to 20 sec     request.Timeout = 20000;       WebResponse response = request.GetResponse();       try     {        Stream strm = response.GetResponseStream();          // Read chunks from the stream and feed load to the image        codecs.StartFeedGetInformation(true, 1);          const int bufferSize = 1024;        byte[] buffer = new byte[bufferSize];          bool more;          do        {           Application.DoEvents();             int read = strm.Read(buffer, 0, bufferSize);           Console.WriteLine("Downloading {0} bytes", read);           if(read > 0)              more = codecs.FeedGetInformation(buffer, 0, read);           else           {              // no more image data in the stream              more = false;           }        }        while(more);     }     finally     {        response.Close();     }       CodecsImageInfo info = codecs.StopFeedGetInformation();       // Clean up     codecs.Dispose();     RasterCodecs.Shutdown();       // Show the information     MessageBox.Show(info.ToString());  }

You must call the FeedGetInformation method to supply buffered data, and you must call StopFeedGetInformation when the process is complete.

This file information process is useful when receiving transmitted images, such as those on the Internet. It works the same way as the GetInformation method, except that your code supplies the image data. The file information process works as follows:

1. You call the StartFeedGetInformation method to initialize the file information process.

2. You create a buffer, and each time you fill it with information, you call the FeedGetInformation method, which sends the data to the file information process just as if the data were being read from a file on disk.

   If the FeedGetInformation returns true, this means the frameworks does not have enough data to get the information required; you must read more data and call the FeedGetInformation again. When FeedGetInformation returns false, the framework has gathered enough data and you can break out of the loop.

3. At any time after calling StartFeedGetInformation, you can call CancelFeedGetInformation to gracefully abort the feed operation. This allows you to end the feed process without throwing an exception.
4. To end the file information process, you call the StopFeedGetInformation method, which cleans up the process, and returns an instance of the CodecsImageInfo class if successful. If you call this method before enough image data is passed to gather the information, it will successfully clean up the process, but will throw an exception. You should catch the exception if the process is canceled purposely.

This method cannot be used in combination with StartRedirecting.

Specifying true for totalPages can cause the process to be slow for files with large number of pages.

Target Platforms: Microsoft .NET Framework 3.0, Windows XP, Windows Server 2003 family, Windows Server 2008 family

Reference