LEADTOOLS Image File Support (Leadtools.Codecs assembly) Send comments on this topic. | Back to Introduction - All Topics | Help Version 17.0.3.29
LoadAsync(Stream,Int32,CodecsLoadByteOrder,Int32,Int32,Object) Method
See Also 
Leadtools.Codecs Namespace > RasterCodecs Class > LoadAsync Method : LoadAsync(Stream,Int32,CodecsLoadByteOrder,Int32,Int32,Object) Method



stream
A System.IO.Stream containing the image data to load.
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 stream.
userState
A user-defined object that is passed to the method invoked when the asynchronous operation completes.
stream
A System.IO.Stream containing the image data to load.
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 stream.
userState
A user-defined object that is passed to the method invoked when the asynchronous operation completes.
Loads the specified image stream using specific options asynchronously.

Syntax

Visual Basic (Declaration) 
Overloads Public Function LoadAsync( _
   ByVal stream As Stream, _
   ByVal bitsPerPixel As Integer, _
   ByVal order As CodecsLoadByteOrder, _
   ByVal firstPage As Integer, _
   ByVal lastPage As Integer, _
   ByVal userState As Object _
) As RasterImage
Visual Basic (Usage)Copy Code
Dim instance As RasterCodecs
Dim stream As Stream
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(stream, bitsPerPixel, order, firstPage, lastPage, userState)
C# 
public RasterImage LoadAsync( 
   Stream stream,
   int bitsPerPixel,
   CodecsLoadByteOrder order,
   int firstPage,
   int lastPage,
   object userState
)
C++/CLI 
public:
RasterImage^ LoadAsync( 
   Stream^ stream,
   int bitsPerPixel,
   CodecsLoadByteOrder order,
   int firstPage,
   int lastPage,
   Object^ userState
)

Parameters

stream
A System.IO.Stream containing the image data to load.
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 stream.
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.

Example

Visual BasicCopy Code
Public Sub LoadAsyncStream2Example()
      Dim srcFileName As String = Path.Combine(LEAD_VARS.ImagesDir, "Ocr1.tif")

      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 LoadAsyncStream2Example_LoadAsyncCompleted
      Dim stream As Stream = File.OpenRead(srcFileName)
      Dim rasterImageObject As Object = codecs.LoadAsync(stream, 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 LoadAsyncStream2Example_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 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 LoadAsyncStream2Example_LoadAsyncCompleted
      codecs.Dispose()
   End Sub

Public NotInheritable Class LEAD_VARS
   Public Const ImagesDir As String = "C:\Users\Public\Documents\LEADTOOLS Images"
End Class
C#Copy Code
public void LoadAsyncStream2Example()
   {
      string srcFileName = Path.Combine(LEAD_VARS.ImagesDir, "Ocr1.tif");

      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>(LoadAsyncStream2Example_LoadAsyncCompleted);
      Stream stream = File.OpenRead(srcFileName);
      object rasterImageObject = codecs.LoadAsync(stream, 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 LoadAsyncStream2Example_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 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>(LoadAsyncStream2Example_LoadAsyncCompleted);
      codecs.Dispose();
   }

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


SilverlightVBCopy Code


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



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 options 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 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.



It is recommended that you do not poll for the RasterImage.IsLoading property to check when the image is finished loaded, instead, subscribe to the LoadAsyncCompleted event to get notification on when the RasterCodecs.LoadAsync operation is completed and if 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: Silverlight, Windows XP, Windows Server 2003 family, Windows Server 2008 family, Windows Vista, Windows 7, MAC OS/X (Intel Only) 

            
            
See Also