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LoadAsync(Stream,int,object) Method

Summary

Loads the specified page from an image stream using default options asynchronously.

Syntax

C#
VB
Java
Objective-C
C++
public RasterImage LoadAsync( 
   Stream stream, 
   int pageNumber, 
   object userState 
) 

Public Overloads Function LoadAsync( _ 
   ByVal stream As Stream, _ 
   ByVal pageNumber As Integer, _ 
   ByVal userState As Object _ 
) As RasterImage 

- (void)loadStreamAsync:(LTLeadStream *)stream  
             pageNumber:(NSInteger)pageNumber  
             completion:(void (^)(LTRasterImage * __nullable image, NSError * __nullable error))completion 

public Object loadAsync(ILeadStream stream, int pageNumber, Object userState) 

public: 
RasterImage^ LoadAsync(  
   Stream^ stream, 
   int pageNumber, 
   Object^ userState 
)  

Parameters

stream
A Stream containing the image data to load.

pageNumber
The 1-based page number.

userState
A user-defined object that is passed to the method invoked when the asynchronous operation completes.

Return Value

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

Remarks

NOTE: This topic is part of RasterCodecs Async support using the .NET System.ComponentMode.AsyncOperation model. For .NET async/await, use Task<RasterImage> LoadAsync(ILeadStream stream, int pageNumber).

The stream can point to any supported image file format and bits per pixel, whether compressed or uncompressed.

This method will load a single page from a multi-page file. The resulting image will have the same bits/pixel and color order value of the image as it was stored in the stream.

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.4

The RasterCodecs class supports loading image files asynchronously using the LoadAsync methods. When calling any of these methods, the caller's thread will not be blocked and the method will return instantly with an instance of 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 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 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.

Requirements

Target Platforms

Help Version 20.0.2018.6.21
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