Loads the specified page from an image URL using default options asynchronously.
Public Overloads Function LoadAsync( _
ByVal uri As Uri, _
ByVal pageNumber As Integer, _
ByVal userState As Object _
) As RasterImage
The Uri containing the input image data.
1-based page number to load.
A user-defined object that is passed to the method invoked when the asynchronous operation completes.
The RasterImage object that this method loads. See remarks for the usage of this object.
NOTE: This topic is part of
RasterCodecs Async support using the .NET
System.ComponentMode.AsyncOperation model. For .NET
use Task<RasterImage> LoadAsync(ILeadStream stream, int pageNumber).
The file can be in any supported image file format and bits per pixel, whether compressed or uncompressed.
This method will load a single page from a multipage file. The resulting image will have the same bits/pixel and color order value of the image as it was stored in the file.
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 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.
LEADTOOLS supports the following URI schemes:
|UriSchemeFile||Specifies that the URI is a disk file in local machine or universal naming convention (UNC) path.|
|UriSchemeHttp||Specifies that the URI is accessed through the Hypertext Transfer Protocol (HTTP).|
|UriSchemeHttps||Specifies that the URI is accessed through the Secure Hypertext Transfer Protocol (HTTPS).|
|UriSchemeFtp||Specifies that the URI is accessed through the File Transfer Protocol (FTP).|
If uri points to a resource in a UriSchemeHttp, UriSchemeHttps or UriSchemeFtp, then this RasterCodecs will attempt to download image data in an iterative fashion by creating a temporary buffer. The size of this buffer can be determined and changed by setting up the UriOperationBufferSize prior to calling this method.
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.
For an example, refer to LoadAsyncCompleted.
Medical Web Viewer .NET
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