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LEADTOOLS Image File Support (Leadtools.Codecs assembly)
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StartRedirecting Method








Leadtools.Codecs Namespace > RasterCodecs Class : StartRedirecting Method
Starts file I/O redirection.
Syntax
public void StartRedirecting()
'Declaration
 

Public Sub StartRedirecting() 
'Usage
 

Dim instance As RasterCodecs
 
instance.StartRedirecting()
public void StartRedirecting()
public void startRedirecting()
 function Leadtools.Codecs.RasterCodecs.StartRedirecting()

public:
void StartRedirecting();
Remarks

LEADTOOLS I/O redirection allows you to replace the default input/output methods for opening, reading, writing, seeking, and closing files.

For example, you can redirect all the library I/O methods to your own I/O methods to load/save images from your own streams.

Once you call StartRedirecting, all subsequent file I/O operation will fire the following events:

Event Operation
RedirectOpen When the toolkit is trying to open a file
RedirectRead When the toolkit is trying to reading from a file
RedirectWrite When the toolkit is trying to writing to a file
RedirectSeek When the toolkit is trying to seeking into a file
RedirectClose When the toolkit is trying to closing a file

Call StopRedirecting to reset the I/O methods back to the defaults.

Example

This example demonstrates overriding the default IO routines.

Copy Code   
Imports Leadtools
Imports Leadtools.Codecs
Imports Leadtools.ImageProcessing
Imports Leadtools.ImageProcessing.Color
Imports Leadtools.Drawing
Imports Leadtools.Svg

' Redirect Read event example
Private myStream As FileStream
' Redirect Open event example
Private Sub Codecs_Open(ByVal sender As Object, ByVal e As CodecsRedirectOpenEventArgs)
   myStream = New FileStream(e.FileName, e.Mode)
   e.Success = True
End Sub

' Redirect Seek event example
Private Sub Codecs_Seek(ByVal sender As Object, ByVal e As CodecsRedirectSeekEventArgs)
   myStream.Seek(e.Offset, e.Origin)
   e.Offset = myStream.Position
End Sub

' Redirect Read event example
Private Sub Codecs_Read(ByVal sender As Object, ByVal e As CodecsRedirectReadEventArgs)
   Dim byteBuffer As Byte() = New Byte(e.Count - 1) {}
   myStream.Read(byteBuffer, 0, e.Count)
   Marshal.Copy(byteBuffer, 0, e.Buffer, e.Count)
   e.Read = e.Count
   Console.WriteLine("The number of bytes that read request should copy to the buffer is : {0}", e.Count)
   Console.WriteLine("The actual number of bytes that this read request has copied to Buffer is : {0}", e.Read)
End Sub

' Redirect Write event example
Private Sub Codecs_Write(ByVal sender As Object, ByVal e As CodecsRedirectWriteEventArgs)
   Dim byteBuffer As Byte() = New Byte(e.Count - 1) {}
   Marshal.Copy(e.Buffer, byteBuffer, 0, e.Count)
   myStream.Write(byteBuffer, 0, e.Count)
   e.Written = e.Count

   Console.WriteLine("The number of bytes that write request should copy from the buffer is : {0}", e.Count)
   Console.WriteLine("The actual number of bytes that this write request has copied from Buffer is : {0}", e.Written)
End Sub

' Redirect Close event example
Private Sub Codecs_Close(ByVal sender As Object, ByVal e As CodecsRedirectCloseEventArgs)
   myStream.Close()
End Sub

      
Public Sub StartRedirectingExample()
   Dim codecs As RasterCodecs = New RasterCodecs()

   AddHandler codecs.RedirectOpen, AddressOf Codecs_Open
   AddHandler codecs.RedirectSeek, AddressOf Codecs_Seek
   AddHandler codecs.RedirectRead, AddressOf Codecs_Read
   AddHandler codecs.RedirectWrite, AddressOf Codecs_Write
   AddHandler codecs.RedirectClose, AddressOf Codecs_Close

   Dim srcFilename As String = Path.Combine(LEAD_VARS.ImagesDir, "Image1.cmp")

   codecs.StartRedirecting()
   Dim image As RasterImage = codecs.Load(srcFilename)
   myStream.Close()
   codecs.Save(image, Path.Combine(LEAD_VARS.ImagesDir, "Image1_redirect.jpg"), RasterImageFormat.Jpeg, image.BitsPerPixel)
   codecs.StopRedirecting()

   ' Clean up
   myStream.Dispose()
   image.Dispose()
   codecs.Dispose()
End Sub

Public NotInheritable Class LEAD_VARS
Public Const ImagesDir As String = "C:\Users\Public\Documents\LEADTOOLS Images"
End Class
using Leadtools;
using Leadtools.Codecs;
using Leadtools.ImageProcessing;
using Leadtools.ImageProcessing.Color;
using Leadtools.Svg;

// Redirect Read event example
FileStream myStream;
// Redirect Open event example
private void Codecs_Open(object sender, CodecsRedirectOpenEventArgs e)
{
   myStream = new FileStream(e.FileName, e.Mode);
   e.Success = true;
}

// Redirect Seek event example
private void Codecs_Seek(object sender, CodecsRedirectSeekEventArgs e)
{
   myStream.Seek(e.Offset, e.Origin);
   e.Offset = myStream.Position;
}

// Redirect Read event example
private void Codecs_Read(object sender, CodecsRedirectReadEventArgs e)
{
   byte[] byteBuffer = new byte[e.Count];
   myStream.Read(byteBuffer, 0, e.Count);
   Marshal.Copy(byteBuffer, 0, e.Buffer, e.Count);
   e.Read = e.Count;
   Console.WriteLine("The number of bytes that read request should copy to the buffer is : {0}", e.Count);
   Console.WriteLine("The actual number of bytes that this read request has copied to Buffer is : {0}", e.Read);
}

// Redirect Write event example
private void Codecs_Write(object sender, CodecsRedirectWriteEventArgs e)
{
   byte[] byteBuffer = new byte[e.Count];
   Marshal.Copy(e.Buffer, byteBuffer, 0, e.Count);
   myStream.Write(byteBuffer, 0, e.Count);
   e.Written = e.Count;

   Console.WriteLine("The number of bytes that write request should copy from the buffer is : {0}", e.Count);
   Console.WriteLine("The actual number of bytes that this write request has copied from Buffer is : {0}", e.Written);
}

// Redirect Close event example
private void Codecs_Close(object sender, CodecsRedirectCloseEventArgs e)
{
   myStream.Close();
}

      
public void StartRedirectingExample()
{
   RasterCodecs codecs = new RasterCodecs();

   codecs.RedirectOpen += new EventHandler<CodecsRedirectOpenEventArgs>(Codecs_Open);
   codecs.RedirectSeek += new EventHandler<CodecsRedirectSeekEventArgs>(Codecs_Seek);
   codecs.RedirectRead += new EventHandler<CodecsRedirectReadEventArgs>(Codecs_Read);
   codecs.RedirectWrite += new EventHandler<CodecsRedirectWriteEventArgs>(Codecs_Write);
   codecs.RedirectClose += new EventHandler<CodecsRedirectCloseEventArgs>(Codecs_Close);

   string srcFilename = Path.Combine(LEAD_VARS.ImagesDir, "Image1.cmp");

   codecs.StartRedirecting();
   RasterImage image = codecs.Load(srcFilename);
   myStream.Close();
   codecs.Save(image, Path.Combine(LEAD_VARS.ImagesDir, "Image1_redirect.jpg"), RasterImageFormat.Jpeg, image.BitsPerPixel);
   codecs.StopRedirecting();

   // Clean up
   myStream.Dispose();
   image.Dispose();
   codecs.Dispose();
}

static class LEAD_VARS
{
public const string ImagesDir = @"C:\Users\Public\Documents\LEADTOOLS Images";
}
Requirements

Target Platforms

See Also

Reference

RasterCodecs Class
RasterCodecs Members

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