LoadAsync(Uri,Int32,CodecsLoadByteOrder,Int32,Int32,Object) Method

Visual Basic
C#
WinRT C#
WinRT JavaScript
C++

public RasterImage LoadAsync( 
   Uri uri,
   int bitsPerPixel,
   CodecsLoadByteOrder order,
   int firstPage,
   int lastPage,
   object userState
)

'Declaration
 
Public Overloads Function LoadAsync( _
   ByVal uri As Uri, _
   ByVal bitsPerPixel As Integer, _
   ByVal order As CodecsLoadByteOrder, _
   ByVal firstPage As Integer, _
   ByVal lastPage As Integer, _
   ByVal userState As Object _
) As RasterImage

'Usage
 
Dim instance As RasterCodecs
Dim uri As Uri
Dim bitsPerPixel As Integer
Dim order As CodecsLoadByteOrder
Dim firstPage As Integer
Dim lastPage As Integer
Dim userState As Object
Dim value As RasterImage
 
value = instance.LoadAsync(uri, bitsPerPixel, order, firstPage, lastPage, userState)

public RasterImage LoadAsync( 
   Uri uri,
   int bitsPerPixel,
   CodecsLoadByteOrder order,
   int firstPage,
   int lastPage,
   object userState
)

 function Leadtools.Codecs.RasterCodecs.LoadAsync(Uri,Int32,CodecsLoadByteOrder,Int32,Int32,Object)( 
   uri ,
   bitsPerPixel ,
   order ,
   firstPage ,
   lastPage ,
   userState 
)

public:
RasterImage^ LoadAsync( 
   Uri^ uri,
   int bitsPerPixel,
   CodecsLoadByteOrder order,
   int firstPage,
   int lastPage,
   Object^ userState
)

Parameters

uri

The System.Uri containing the input image data.

bitsPerPixel

Resulting image pixel depth. Valid values are:

Value	Meaning
0	Keep the original file's pixel depth (Do not convert).
1 to 8	The specified bits per pixel in the resulting image.
12	12 bits per pixel in the resulting image.
16	16 bits per pixel in the resulting image.
24	24 bits per pixel in the resulting image.
32	32 bits per pixel in the resulting image.
48	48 bits per pixel in the resulting image.
64	64 bits per pixel in the resulting image.

order

Color order for 16-, 24-, 32-, 48-, and 64-bit images. If the resulting image is less than 16 bits per pixel, this will have no effect since palletized images have no order. The following are valid values.

Value	Meaning
CodecsLoadByteOrder.Rgb	Red, green, and blue color order in memory
CodecsLoadByteOrder.Bgr	Blue, green, and red color order in memory
CodecsLoadByteOrder.Gray	12 or 16-bit grayscale image. 12 and 16-bit grayscale images are only supported in the Document/Medical Imaging editions.
CodecsLoadByteOrder.RgbOrGray	Load the image as red, green, blue OR as a 12 or 16-bit grayscale image. 12 and 16-bit grayscale images are supported in the Document/Medical Imaging editions
CodecsLoadByteOrder.BgrOrGray	Load the image as blue, green, red OR as a 12 or 16-bit grayscale image. 12 and 16-bit grayscale images are supported in the Document/Medical Imaging editions
CodecsLoadByteOrder.Romm	ROMM order. ROMM only supports 24 and 48-bit images
CodecsLoadByteOrder.BgrOrGrayOrRomm	Load the image as red, green, blue OR as a 12 or 16-bit grayscale image OR as ROMM. 12 and 16-bit grayscale images are supported in the Document/Medical Imaging editions only. ROMM only supports 24 and 48-bit color images.

firstPage

1-based index of the first page to load.

lastPage

The 1-based index of the last page to load. Must be greater than or equal to firstPage. You can pass -1 to load from firstPage to the last page in the file.

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.

The file can be in any supported image file format and bits per pixel, whether compressed or uncompressed.

This method will load all the pages in 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 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.

LEADTOOLS supports the following URI schemes:

Scheme	Description
System.Uri.UriSchemeFile	Specifies that the URI is a disk file in local machine or universal naming convention (UNC) path.
System.Uri.UriSchemeHttp	Specifies that the URI is accessed through the Hypertext Transfer Protocol (HTTP).
System.Uri.UriSchemeHttps	Specifies that the URI is accessed through the Secure Hypertext Transfer Protocol (HTTPS).
System.Uri.UriSchemeFtp	Specifies that the URI is accessed through the File Transfer Protocol (FTP).

If uri points to a resource in a System.Uri.UriSchemeHttp, System.Uri.UriSchemeHttps or System.Uri.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.

For authenticity and proxy settings, refer to UriOperationCredentials and UriOperationProxy.

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.

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

Public Sub LoadAsyncUrl1Example()
      Dim srcFileName As String = Path.Combine(LEAD_VARS.ImagesDir, "Ocr1.tif")
      Dim uri As New Uri(srcFileName)

      Dim codecs As New RasterCodecs()

      ' Now load the first page of the image as 24 bits/pixel with order BGR asynchronously
      AddHandler codecs.LoadAsyncCompleted, AddressOf LoadAsyncUrl1Example_LoadAsyncCompleted
      Dim rasterImageObject As Object = codecs.LoadAsync(uri, 24, CodecsLoadByteOrder.BgrOrGray, 1, 1, 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 LoadAsyncUrl1Example_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 at {0} loaded OK, size: {1} by {2}, order: {3}, bits/pixel: {4}", e.Uri, image.Width, image.Height, image.Order, image.BitsPerPixel)
         image.Dispose()
      End If

      ' Unsubscribe to the event and dispose the RasterCodecs object
      Dim codecs As RasterCodecs = DirectCast(sender, RasterCodecs)
      RemoveHandler codecs.LoadAsyncCompleted, AddressOf LoadAsyncUrl1Example_LoadAsyncCompleted
      codecs.Dispose()
   End Sub

Public NotInheritable Class LEAD_VARS
   Public Const ImagesDir As String = "C:\Users\Public\Documents\LEADTOOLS Images"
End Class

public void LoadAsyncUrl1Example()
     {
         string srcFileName = Path.Combine(LEAD_VARS.ImagesDir, "Ocr1.tif");
         Uri uri = new Uri(srcFileName);

         RasterCodecs codecs = new RasterCodecs();

         // Now load the first page of the image as 24 bits/pixel with order BGR asynchronously
         codecs.LoadAsyncCompleted += new EventHandler<CodecsLoadAsyncCompletedEventArgs>(LoadAsyncUrl1Example_LoadAsyncCompleted);
         object rasterImageObject = codecs.LoadAsync(uri, 24, CodecsLoadByteOrder.BgrOrGray, 1, 1, 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 LoadAsyncUrl1Example_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 at {0} loaded OK, size: {1} by {2}, order: {3}, bits/pixel: {4}", e.Uri, image.Width, image.Height, image.Order, image.BitsPerPixel);
             image.Dispose();
         }

         // Unsubscribe to the event and dispose the RasterCodecs object
         RasterCodecs codecs = sender as RasterCodecs;
         codecs.LoadAsyncCompleted -= new EventHandler<CodecsLoadAsyncCompletedEventArgs>(LoadAsyncUrl1Example_LoadAsyncCompleted);
         codecs.Dispose();
     }

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

Target Platforms: Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

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