StartFeedLoad(int,CodecsLoadByteOrder,int,int) Method

Summary

Initializes a file-load process in which you control the input stream with specific number of pages.

Syntax

Objective-C

C++/CLI

Java

Python

public void StartFeedLoad( 
   int bitsPerPixel, 
   CodecsLoadByteOrder order, 
   int firstPage, 
   int lastPage 
)

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

public FeedCallbackThunk startFeedLoad(int bitsPerPixel, CodecsLoadByteOrder order, int firstPage, int lastPage)

public: 
void StartFeedLoad(  
   int bitsPerPixel, 
   CodecsLoadByteOrder order, 
   int firstPage, 
   int lastPage 
)

def StartFeedLoad(self,bitsPerPixel,order,firstPage,lastPage):

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.

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 file.

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.
You can also call the IsFeedLoadDone property to determine whether the framework has enough data to load the pages specified in firstPage and lastPage.

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.

Example

This example will use feed load to load a few pages of a multipage file

Java

using Leadtools; 
using Leadtools.Codecs; 
using Leadtools.ImageProcessing; 
using Leadtools.ImageProcessing.Color; 
using Leadtools.Svg; 
 
 
public void FeedLoadMultiExample() 
{ 
   RasterCodecs codecs = new RasterCodecs(); 
 
   string srcFileName = Path.Combine(LEAD_VARS.ImagesDir, "Eye.gif"); 
   string destFileName = Path.Combine(LEAD_VARS.ImagesDir, "FeedLoadMulti.tif"); 
 
   // Load pages 2 through 5 from the file by reading chunks from the stream 
   codecs.StartFeedLoad(0, CodecsLoadByteOrder.BgrOrGray, 2, 5); 
 
   using (FileStream fs = File.OpenRead(srcFileName)) 
   { 
      const int bufferSize = 1024; 
      byte[] buffer = new byte[bufferSize]; 
 
      int read; 
 
      do 
      { 
         System.Windows.Forms.Application.DoEvents(); 
 
         read = fs.Read(buffer, 0, bufferSize); 
         Debug.WriteLine("Feeding {0} bytes", read); 
         if (read > 0) 
            codecs.FeedLoad(buffer, 0, read); 
      } 
      while (read > 0 && !codecs.IsFeedLoadDone); 
   } 
 
   RasterImage image = codecs.StopFeedLoad(); 
   Debug.WriteLine("{0} pages loaded", image.PageCount); 
 
   // Save the image to disk 
   codecs.Save(image, destFileName, RasterImageFormat.Tif, 1, 1, -1, 1, CodecsSavePageMode.Overwrite); 
   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 feedLoadMultiExample() throws IOException { 
   final String LEAD_VARS_IMAGES_DIR = "C:\\LEADTOOLS23\\Resources\\Images"; 
   RasterCodecs codecs = new RasterCodecs(); 
 
   String srcFileName = combine(LEAD_VARS_IMAGES_DIR, "Eye.gif"); 
   String destFileName = combine(LEAD_VARS_IMAGES_DIR, "FeedLoadMulti.tif"); 
 
   // Load pages 2 through 5 from the file by reading chunks from the stream 
   FeedCallbackThunk feedLoad = codecs.startFeedLoad(0, CodecsLoadByteOrder.BGR_OR_GRAY, 2, 5); 
 
   try (InputStream fileStream = new FileInputStream(srcFileName)) { 
      final int bufferSize = 1024; 
      byte[] buffer = new byte[bufferSize]; 
      int read = 0; 
 
      do { 
         read = fileStream.read(buffer, 0, bufferSize); 
         System.out.println("Feeding " + read + " bytes"); 
         if (read > 0) 
            feedLoad.feedLoad(buffer, 0, read); 
      } while (read > 0 && !feedLoad.isFeedLoadDone()); 
   } 
   RasterImage image = feedLoad.stopFeedLoad(); 
   System.out.println(image.getPageCount() + " pages loaded"); 
 
   // Save the image to disk 
   codecs.save(image, destFileName, RasterImageFormat.TIF, 1, 1, -1, 1, CodecsSavePageMode.OVERWRITE); 
   assertTrue("Image unsuccessfully saved", (new File(destFileName)).exists()); 
   System.out.println("Saved image at" + destFileName); 
 
   // Clean up 
   image.dispose(); 
   codecs.dispose(); 
}