Loads the specified rectangle from the specified image file using default options asynchronously.
public RasterImage LoadAsync(
string fileName,
LeadRect tile,
object userState
)
Public Overloads Function LoadAsync( _
ByVal fileName As String, _
ByVal tile As LeadRect, _
ByVal userState As Object _
) As RasterImage
public:
RasterImage^ LoadAsync(
String^ fileName,
LeadRect tile,
Object^ userState
)
fileName
A String containing the name of the image file to load.
tile
A 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.
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 async/await
support this type/member is not used. Instead, refer to RasterCodecs Async Operations.
This method loads a section of an image file (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 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 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.
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.
using Leadtools;
using Leadtools.Codecs;
using Leadtools.ImageProcessing;
using Leadtools.ImageProcessing.Color;
using Leadtools.Svg;
using LeadtoolsExamples.Common;
public void LoadAsyncFile3Example()
{
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>(LoadAsyncFile3Example_LoadAsyncCompleted);
object rasterImageObject = codecs.LoadAsync(srcFileName, 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 LoadAsyncFile3Example_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.FileName, 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>(LoadAsyncFile3Example_LoadAsyncCompleted);
codecs.Dispose();
}
static class LEAD_VARS
{
public const string ImagesDir = @"C:\Users\Public\Documents\LEADTOOLS Images";
}
Imports Leadtools
Imports Leadtools.Codecs
Imports Leadtools.ImageProcessing
Imports Leadtools.ImageProcessing.Color
Imports Leadtools.Drawing
Imports Leadtools.Svg
Public Sub LoadAsyncFile3Example()
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 LoadAsyncFile3Example_LoadAsyncCompleted
Dim rasterImageObject As Object = codecs.LoadAsync(srcFileName, 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 LoadAsyncFile3Example_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.FileName, 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 LoadAsyncFile3Example_LoadAsyncCompleted
codecs.Dispose()
End Sub
Public NotInheritable Class LEAD_VARS
Public Const ImagesDir As String = "C:\Users\Public\Documents\LEADTOOLS Images"
End Class
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