Leadtools.Codecs Namespace > RasterCodecs Class > LoadAsync Method : LoadAsync(String,Int32,Object) Method |
public RasterImage LoadAsync( string fileName, int pageNumber, object userState )
'Declaration Public Overloads Function LoadAsync( _ ByVal fileName As String, _ ByVal pageNumber As Integer, _ ByVal userState As Object _ ) As RasterImage
'Usage Dim instance As RasterCodecs Dim fileName As String Dim pageNumber As Integer Dim userState As Object Dim value As RasterImage value = instance.LoadAsync(fileName, pageNumber, userState)
public RasterImage LoadAsync( string fileName, int pageNumber, object userState )
function Leadtools.Codecs.RasterCodecs.LoadAsync(String,Int32,Object)( fileName , pageNumber , userState )
public: RasterImage^ LoadAsync( String^ fileName, int pageNumber, Object^ userState )
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 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 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.
Imports Leadtools Imports Leadtools.Codecs Imports Leadtools.ImageProcessing Imports Leadtools.ImageProcessing.Color Imports Leadtools.Drawing Class LoadPagesFromFileAsyncTestData Public PageCount As Integer Public PageNumber As Integer End Class Private Shared Sub LoadPagesFromFileAsyncTest(fileName As String) ' Create a new RasterCodecs instance, we will dispose it when the images finish loading Dim rasterCodecs As New RasterCodecs() ' Create the data Dim data As New LoadPagesFromFileAsyncTestData() ' Get the number of pages data.PageCount = rasterCodecs.GetTotalPages(fileName) Console.WriteLine("Number of pages in the file is {0}", data.PageCount) ' Load all pages asynchrounsly data.PageNumber = 1 ' Start with the first page, then load next when operation finishes AddHandler rasterCodecs.LoadAsyncCompleted, AddressOf rasterCodecs_LoadAsyncCompleted rasterCodecs.LoadAsync(fileName, data.PageNumber, data) End Sub Private Shared Sub rasterCodecs_LoadAsyncCompleted(sender As Object, e As CodecsLoadAsyncCompletedEventArgs) ' A page is loaded, show info Dim data As LoadPagesFromFileAsyncTestData = CType(e.UserState, LoadPagesFromFileAsyncTestData) Console.WriteLine("Page {0} loaded", data.PageNumber) ' If there is an error, show it If Not IsNothing(e.Error) Then Console.WriteLine("Error {0}", e.Error.Message) End If ' Dispose the image If Not IsNothing(e.Image) Then e.Image.Dispose() End If ' Get the raster codecs instance Dim rasterCodecs As RasterCodecs = CType(sender, RasterCodecs) If data.PageNumber < data.PageCount Then ' Load next Console.WriteLine("Load next") data.PageNumber = data.PageNumber + 1 rasterCodecs.LoadAsync(e.FileName, data.PageNumber, data) Else ' Finished loading, clean up Console.WriteLine("Finished") RemoveHandler rasterCodecs.LoadAsyncCompleted, AddressOf rasterCodecs_LoadAsyncCompleted rasterCodecs.Dispose() End If End Sub
using Leadtools; using Leadtools.Codecs; using Leadtools.ImageProcessing; using Leadtools.ImageProcessing.Color; class LoadPagesFromFileAsyncTestData { public int PageCount; public int PageNumber; } private static void LoadPagesFromFileAsyncTest(string fileName) { // Create a new RasterCodecs instance, we will dispose it when the images finish loading RasterCodecs rasterCodecs = new RasterCodecs(); // Create the data LoadPagesFromFileAsyncTestData data = new LoadPagesFromFileAsyncTestData(); // Get the number of pages data.PageCount = rasterCodecs.GetTotalPages(fileName); Console.WriteLine("Number of pages in the file is {0}", data.PageCount); // Load all pages asynchrounsly data.PageNumber = 1; // Start with the first page, then load next when operation finishes rasterCodecs.LoadAsyncCompleted += new EventHandler<CodecsLoadAsyncCompletedEventArgs>(rasterCodecs_LoadAsyncCompleted); rasterCodecs.LoadAsync(fileName, data.PageNumber, data); } private static void rasterCodecs_LoadAsyncCompleted(object sender, CodecsLoadAsyncCompletedEventArgs e) { // A page is loaded, show info LoadPagesFromFileAsyncTestData data = e.UserState as LoadPagesFromFileAsyncTestData; Console.WriteLine("Page {0} loaded", data.PageNumber); // If there is an error, show it if (e.Error != null) Console.WriteLine("Error {0}", e.Error.Message); // Dispose the image if (e.Image != null) e.Image.Dispose(); // Get the raster codecs instance RasterCodecs rasterCodecs = sender as RasterCodecs; if (data.PageNumber < data.PageCount) { // Load next Console.WriteLine("Load next"); data.PageNumber++; rasterCodecs.LoadAsync(e.FileName, data.PageNumber, data); } else { // Finished loading, clean up Console.WriteLine("Finished"); rasterCodecs.LoadAsyncCompleted -= new EventHandler<CodecsLoadAsyncCompletedEventArgs>(rasterCodecs_LoadAsyncCompleted); rasterCodecs.Dispose(); } }