LoadAsync(Stream,LeadRect,Object) Method

C#
Visual Basic
WinRT C#
Objective-C
Java
WinRT JavaScript
C++

public RasterImage LoadAsync( 
   Stream stream,
   LeadRect tile,
   object userState
)

'Declaration
 
Public Overloads Function LoadAsync( _
   ByVal stream As Stream, _
   ByVal tile As LeadRect, _
   ByVal userState As Object _
) As RasterImage

'Usage
 
Dim instance As RasterCodecs
Dim stream As Stream
Dim tile As LeadRect
Dim userState As Object
Dim value As RasterImage
 
value = instance.LoadAsync(stream, tile, userState)

public RasterImage LoadAsync( 
   Stream stream,
   LeadRect tile,
   object userState
)

public Object loadAsync(ILeadStream stream, LeadRect tile, Object userState)

 function Leadtools.Codecs.RasterCodecs.LoadAsync(Stream,LeadRect,Object)( 
   stream ,
   tile ,
   userState 
)

public:
RasterImage^ LoadAsync( 
   Stream^ stream,
   LeadRect tile,
   Object^ userState
)

Parameters

stream: A System.IO.Stream containing the image data to load.
tile: A Leadtools.LeadRect describing the tile/area of the image to load.
userState: A user-defined object that is passed to the method invoked when the asynchronous operation completes.

Return Value

The Leadtools.RasterImage object that this method loads. See remarks for the usage of this object.

This method loads a section of an image stream (any format). The section begins is defined by tile rectangle.

LEADTOOLS will attempt to load corrupted files so you can see at least a portion of the image. For these images, the load methods succeed, but LoadStatus will return an error code.

Use the CodecsLoadOptions class to set up other load option parameters before calling this method.

Support for 12 and 16-bit grayscale images is only available in the Document/Medical Imaging editions.

For supported formats, refer to Summary of All Supported Image File Formats.

LEADTOOLS loads all PDF files as Raster PDF uncompressed RasterImageFormat.RasPdf, regardless of the compression and color space used when saving the file.

The RasterCodecs class supports loading image files asynchronously using the LoadAsync methods. When calling any of these methods, the caller thread will not be blocked and the method will return instantly with an instance of Leadtools.RasterImage that is in a loading status (RasterImage.IsLoading set to true). You should not use the other properties of this object while the object is in loading status.

When the RasterCodecs object finishes loading the image, the various properties of the Leadtools.RasterImage will be populated with the image information and data and the RasterImage.IsLoading property will be set to false.

Do not poll the RasterImage.IsLoading property to determine whether the image has finished loading. Instead, subscribe to the LoadAsyncCompleted event to get notification when the LoadAsync(String,LeadRect,Int32,CodecsLoadByteOrder,Int32,Int32,Object) operation has completed and whether any errors occurred.

The LoadAsyncCompleted event data will also contain the same object returned from LoadAsync so you do not have to keep the original object in your application.

The CodecsLoadOptions.AllPages property controls whether RasterCodecs will try to load all pages or just the first page if the image data contains multiple pages.

C#
Visual Basic
WinRT C#
WinRT JavaScript
Silverlight C#
Silverlight VB

Copy Code

Imports Leadtools
Imports Leadtools.Codecs
Imports Leadtools.ImageProcessing
Imports Leadtools.ImageProcessing.Color
Imports Leadtools.Drawing

Public Sub LoadAsyncStream3Example()
   Dim codecs As New RasterCodecs()

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

   ' Load a random tile from the image asynchronously
   Dim tileRect As New LeadRect(100, 50, 200, 150)
   AddHandler codecs.LoadAsyncCompleted, AddressOf LoadAsyncStream3Example_LoadAsyncCompleted
   Dim stream As Stream = File.OpenRead(srcFileName)
   Dim rasterImageObject As Object = codecs.LoadAsync(stream, tileRect, Nothing)

   ' Notice that the returned rasterImageObject is a RasterImage with IsLoading set to true at this point
   ' The IsLoading will be false (and hence, the object will be usable) when the LoadAsyncCompleteted
   ' fires.
End Sub

Private Sub LoadAsyncStream3Example_LoadAsyncCompleted(ByVal sender As Object, ByVal e As CodecsLoadAsyncCompletedEventArgs)
   If e.Cancelled Then
      Console.WriteLine("User canceled")
   ElseIf Not IsNothing(e.Error) Then
      Console.WriteLine("Error: " + e.Error.Message)
   Else
      ' Everything is OK, get the image
      Dim image As RasterImage = e.Image
      Console.WriteLine("Image loaded OK, size: {0} by {1}, order: {2}, bits/pixel: {3}", image.Width, image.Height, image.Order, image.BitsPerPixel)
      image.Dispose()
   End If

   ' We should close the stream here
   e.Stream.Dispose()

   ' Unsubscribe to the event and dispose the RasterCodecs object
   Dim codecs As RasterCodecs = DirectCast(sender, RasterCodecs)
   RemoveHandler codecs.LoadAsyncCompleted, AddressOf LoadAsyncStream3Example_LoadAsyncCompleted
   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;

public void LoadAsyncStream3Example()
{
   RasterCodecs codecs = new RasterCodecs();

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

   // Load a random tile from the image asynchronously
   LeadRect tileRect = new LeadRect(100, 50, 200, 150);
   codecs.LoadAsyncCompleted += new EventHandler<CodecsLoadAsyncCompletedEventArgs>(LoadAsyncStream3Example_LoadAsyncCompleted);
   Stream stream = File.OpenRead(srcFileName);
   object rasterImageObject = codecs.LoadAsync(stream, tileRect, null);

   // Notice that the returned rasterImageObject is a RasterImage with IsLoading set to true at this point
   // The IsLoading will be false (and hence, the object will be usable) when the LoadAsyncCompleteted
   // fires.
}

private void LoadAsyncStream3Example_LoadAsyncCompleted(object sender, CodecsLoadAsyncCompletedEventArgs e)
{
   if (e.Cancelled)
   {
      Console.WriteLine("User canceled");
   }
   else if (e.Error != null)
   {
      Console.WriteLine("Error: " + e.Error.Message);
   }
   else
   {
      // Everything is OK, get the image
      RasterImage image = e.Image;
      Console.WriteLine("Image loaded OK, size: {0} by {1}, order: {2}, bits/pixel: {3}", image.Width, image.Height, image.Order, image.BitsPerPixel);
      image.Dispose();
   }

   // We should close the stream here
   e.Stream.Dispose();

   // Unsubscribe to the event and dispose the RasterCodecs object
   RasterCodecs codecs = sender as RasterCodecs;
   codecs.LoadAsyncCompleted -= new EventHandler<CodecsLoadAsyncCompletedEventArgs>(LoadAsyncStream3Example_LoadAsyncCompleted);
   codecs.Dispose();
}

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

Target Platforms

Reference

RasterCodecs Class
RasterCodecs Members
Overload List
Loading and Saving Images
Loading and Saving Large Tiff Files
Speeding Up 1-Bit Documents
Fast File Info