StartFeedLoad(int,CodecsLoadByteOrder) Method

Summary

Initializes a file-load process in which you control the input stream.

Syntax

Objective-C

C++/CLI

Java

Python

public void StartFeedLoad( 
   int bitsPerPixel, 
   CodecsLoadByteOrder order 
)

- (BOOL)startFeedLoad:(NSInteger)bitsPerPixel order:(LTCodecsLoadByteOrder)order error:(NSError **)error

public FeedCallbackThunk startFeedLoad(int bitsPerPixel, CodecsLoadByteOrder order)

public: 
void StartFeedLoad(  
   int bitsPerPixel, 
   CodecsLoadByteOrder order 
)

def StartFeedLoad(self,bitsPerPixel,order):

Parameters

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
The desired color order. Possible values are:

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.

Remarks

You must call the FeedLoad method to supply buffered data, and you must call StopFeedLoad when the loading is complete.

This file-load process is useful when receiving transmitted images, such as those on the Internet. It works the same way as the Load or LoadAsync methods, except that your code supplies the image data. The file-load process works as follows:

You call the StartFeedLoad method to initialize the file-load process.
You create a buffer, and each time you fill it with information, you call the FeedLoad method, which sends the data to the file-load process just as if the data were being read from a file on disk.
Whenever it has enough data to do so, the file-load process behaves the same as in the Load or LoadAsync methods. It allocates and begins loading the image. It calls your LoadImage event handler, if one is specified, whenever it has enough data in its input buffer.

The file-load process updates information in the RasterImage when it has received enough information to do so. The file-load process will make the first call to your event handler whenever this information is available.
At any time after calling StartFeedLoad, you can call CancelFeedLoad to gracefully abort the feed load operation. This allows you to end the feed load process without throwing an exception.
To end the file-load process, you call the StopFeedLoad method, which cleans up the process, and returns the loaded RasterImage, if successful. If you call this method before supplying the complete file, it will successfully clean up the process, but will throw an exception. You should catch the exception if the load is canceled purposely.

CodecsLoadByteOrder.Gray is only valid for 12 and 16-bit grayscale images. Support for 12 and 16-bit grayscale images is only available in the Document/Medical Imaging editions.

This method cannot be used in combination with StartRedirecting.

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.

Example

This example will use feed load to load an image from a url

Java

using Leadtools; 
using Leadtools.Codecs; 
using Leadtools.ImageProcessing; 
using Leadtools.ImageProcessing.Color; 
using Leadtools.Svg; 
 
 
public void FeedLoadExample() 
{ 
   RasterCodecs codecs = new RasterCodecs(); 
 
   codecs.CancelFeedLoad(); 
 
   string url = @"https://www.leadtools.com/images/page_graphics/leadlogo.png"; 
   string destFileName = Path.Combine(LEAD_VARS.ImagesDir, "FeedLoad.bmp"); 
 
   // Create a WebRequest for the URL 
   WebRequest request = WebRequest.Create(url); 
   request.Proxy.Credentials = CredentialCache.DefaultCredentials; 
 
   // reduce the timeout to 20sec 
   request.Timeout = 20000; 
 
   WebResponse response = request.GetResponse(); 
   try 
   { 
      Stream strm = response.GetResponseStream(); 
 
      // Read chunks from the stream and feed load to the image 
      codecs.StartFeedLoad(0, CodecsLoadByteOrder.BgrOrGray); 
 
      const int bufferSize = 1024; 
      byte[] buffer = new byte[bufferSize]; 
 
      int read; 
 
      do 
      { 
         System.Windows.Forms.Application.DoEvents(); 
 
         read = strm.Read(buffer, 0, bufferSize); 
         Debug.WriteLine("Downloading {0} bytes", read); 
         if (read > 0) 
            codecs.FeedLoad(buffer, 0, read); 
      } 
      while (read > 0); 
   } 
   finally 
   { 
      response.Close(); 
   } 
 
   RasterImage image = codecs.StopFeedLoad(); 
 
   // Save the image to disk 
   codecs.Save(image, destFileName, RasterImageFormat.Bmp, 24); 
   image.Dispose(); 
 
   // Clean up 
   codecs.Dispose(); 
} 
 
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 feedLoadExample() throws IOException { 
   final String LEAD_VARS_IMAGES_DIR = "C:\\LEADTOOLS23\\Resources\\Images"; 
   RasterCodecs codecs = new RasterCodecs(); 
 
   URL url = new URL("https://www.leadtools.com/images/page_graphics/leadlogo.png"); 
   String destFileName = combine(LEAD_VARS_IMAGES_DIR, "FeedLoad.bmp"); 
 
   // Create a WebRequest for the URL 
   HttpURLConnection con = (HttpURLConnection) url.openConnection(); 
   con.setRequestMethod("GET"); 
   con.setDefaultUseCaches(true); 
   // reduce the timeout to 20sec 
   con.setConnectTimeout(20000); 
   con.setReadTimeout(20000); 
 
   con.getResponseCode(); 
   FeedCallbackThunk feedLoad; 
   try { 
      InputStream requestInput = con.getInputStream(); 
 
      // Read chunks from the stream and feed load to the image 
      feedLoad = codecs.startFeedLoad(0, CodecsLoadByteOrder.BGR_OR_GRAY); 
 
      final int bufferSize = 1024; 
      byte[] buffer = new byte[bufferSize]; 
 
      int read; 
      do { 
         read = requestInput.read(buffer, 0, bufferSize); 
         System.out.println("Downloading " + read + " bytes"); 
         if (read > 0) 
            feedLoad.feedLoad(buffer, 0, read); 
      } while (read > 0); 
      requestInput.close(); 
   } finally { 
      con.disconnect(); 
   } 
 
   RasterImage image = feedLoad.stopFeedLoad(); 
 
   // Save the image to disk 
   codecs.save(image, destFileName, RasterImageFormat.BMP, 24); 
   assertTrue("Image unsuccessfully saved", (new File(destFileName)).exists()); 
   System.out.println("Saved image at" + destFileName); 
 
   // Clean up 
   image.dispose(); 
   codecs.dispose(); 
}