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GetInformationAsync(Stream,bool,int,object) Method


Gets the image information from a stream containing image data asynchronously.

public CodecsImageInfo GetInformationAsync( 
   Stream stream, 
   bool totalPages, 
   int pageNumber, 
   object userState 
- (void)imageInformationForStreamAsync:(LTLeadStream *)stream  
                            completion:(void (^)(LTCodecsImageInfo * __nullable info, NSError * __nullable error))completion 
public Object getInformationAsync(ILeadStream stream, boolean totalPages, int pageNumber, Object userState) 
CodecsImageInfo^ GetInformationAsync(  
   Stream^ stream, 
   bool totalPages, 
   int pageNumber, 
   Object^ userState 
def GetInformationAsync(self,stream,totalPages,pageNumber,userState): 


Stream containing the input image data to query.

true to query the file for total number of pages; false, otherwise.

The page number to query. Pass 1 for the first page (default).

A user-defined object that is passed to the method invoked when the asynchronous operation completes.

Return Value

A CodecsImageInfo object that contains the information about the specified image. See remarks about 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, use Task<CodecsImageInfo> GetInformationAsync(ILeadStream stream, bool totalPages, int pageNumber).

Specifying true for  totalPages can cause the process to be slow for files with large number of pages.

The RasterCodecs class supports getting information on image files asynchronously using the GetInformationAsync methods. When calling any of these methods, the caller thread will not be blocked and the method will return instantly with an instance CodecsImageInfo that is in a loading status (CodecsImageInfo.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 getting the information about the file, the various properties of the CodecsImageInfo will be populated with the image file information and the CodecsImageInfo.IsLoading property will be set to false.

It is recommended that you do not poll for the CodecsImageInfo.IsLoading property to determine whether the image information has been collected. Instead, subscribe to the GetInformationAsyncCompleted event to get notification on when the GetInformationAsync operation is completed and whether any errors occurred.

The GetInformationAsyncCompleted event data will also contain the same object returned from GetInformationAsync so you do not have to keep the original object in your application. userState will be passed to the CodecsGetInformationAsyncCompletedEventArgs.UserState member of the GetInformationAsyncCompleted event data.

using Leadtools; 
using Leadtools.Codecs; 
using Leadtools.ImageProcessing; 
using Leadtools.ImageProcessing.Color; 
using Leadtools.Svg; 
public void GetInformationAsyncStreamExample() 
   string srcFileName = Path.Combine(LEAD_VARS.ImagesDir, "Image1.cmp"); 
   RasterCodecs codecs = new RasterCodecs(); 
   // Now get information about the file asynchronously 
   codecs.GetInformationAsyncCompleted += new EventHandler<CodecsGetInformationAsyncCompletedEventArgs>(GetInformationAsyncStreamExample_GetInformationAsyncCompleted); 
   Stream stream = File.OpenRead(srcFileName); 
   object imageInfoObject = codecs.GetInformationAsync(stream, true, 1, null); 
   // Notice that the returned imageInfoObject is a CodecsImageInfo with IsLoading set to true at this point 
   // The IsLoading will be false (and hence, the object will be usable) when the GetInformationAsyncCompleted 
   // fires. 
private void GetInformationAsyncStreamExample_GetInformationAsyncCompleted(object sender, CodecsGetInformationAsyncCompletedEventArgs e) 
   if (e.Cancelled) 
      Debug.WriteLine("User canceled"); 
   else if (e.Error != null) 
      Debug.WriteLine("Error: " + e.Error.Message); 
      // Get the image info 
      CodecsImageInfo info = e.Info; 
      Debug.WriteLine("Image info obtained asynchronously:\n{0}", info.ToString()); 
   // We should close the stream here 
   // Unsubscribe to the event and dispose the RasterCodecs object 
   RasterCodecs codecs = sender as RasterCodecs; 
   codecs.GetInformationAsyncCompleted -= new EventHandler<CodecsGetInformationAsyncCompletedEventArgs>(GetInformationAsyncStreamExample_GetInformationAsyncCompleted); 
static class LEAD_VARS 
   public const string ImagesDir = @"C:\LEADTOOLS23\Resources\Images"; 
import java.io.*; 
import java.net.*; 
import java.nio.file.Paths; 
import java.util.*; 
import java.time.Instant; 
import java.time.Duration; 
import org.junit.*; 
import org.junit.runner.JUnitCore; 
import org.junit.runner.Result; 
import org.junit.runner.notification.Failure; 
import static org.junit.Assert.*; 
import leadtools.*; 
import leadtools.codecs.*; 
import leadtools.codecs.RasterCodecs.FeedCallbackThunk; 
import leadtools.drawing.internal.*; 
import leadtools.imageprocessing.*; 
import leadtools.imageprocessing.color.ChangeIntensityCommand; 
import leadtools.svg.*; 
public void getInformationAsyncStreamExample() throws IOException { 
   final String LEAD_VARS_IMAGES_DIR = "C:\\LEADTOOLS23\\Resources\\Images"; 
   String srcFileName = combine(LEAD_VARS_IMAGES_DIR, "Image1.cmp"); 
   RasterCodecs codecs = new RasterCodecs(); 
   // Now get information about the file asynchronously 
   ILeadStream stream = LeadStreamFactory.create(srcFileName); 
   codecs.getInformationAsync(stream, true, 1, null); 
   assertTrue("Confirm that information was received", codecs.getInformationAsync(stream, true, 1, null) != null); 
   System.out.println("Information was received"); 
CodecsGetInformationAsyncCompletedListener getInformationAsyncStreamExampleGetInformationAsyncCompleted = new CodecsGetInformationAsyncCompletedListener() { 
   public void onGetInformationAsyncCompleted(CodecsGetInformationAsyncCompletedEvent e) { 
      if (e.getCancelled()) { 
         System.out.println("User canceled"); 
      } else if (e.getError() != null) { 
         System.out.println("Error: " + e.getError().getMessage()); 
      } else { 
         // Get the image info 
         CodecsImageInfo info = e.getInfo(); 
         System.out.println("Image info obtained asynchronously:\n" + info.toString()); 
      // We should close the stream here 
      // Unsubscribe to the event and dispose the RasterCodecs object 
      RasterCodecs codecs = (RasterCodecs) e.getSource(); 

Target Platforms

Help Version 23.0.2024.2.29
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Leadtools.Codecs Assembly

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© 1991-2023 LEAD Technologies, Inc. All Rights Reserved.