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ReadBarcodes(RasterImage,LeadRect,int,BarcodeSymbology[],BarcodeReadOptions[]) Method

Read multiple barcodes from an image with symbologies from a specified group and options.
- (nullable NSArray<LTBarcodeData *> *)readBarcodes:(LTRasterImage *)image searchBounds:(LeadRect)searchBounds maximumBarcodes:(NSUInteger)maximumBarcodes symbologies:(nullable NSArray<NSNumber *> *)symbologies options:(nullable NSArray<LTBarcodeReadOptions *> *)options error:(NSError **)error NS_SWIFT_NOTHROW; 
public BarcodeData[] readBarcodes( 
  RasterImage image,  
  LeadRect searchBounds,  
  int maximumBarcodes,  
  BarcodeSymbology[] symbologies,  
  BarcodeReadOptions[] options 


A RasterImage object that contains the image data. Must not be null (Nothing in VB).

A LeadRect that specifies the region of interest area in the image where the barcodes search and detection is performed. You can specify LeadRect.Empty to indicate that the search must be performed on the whole image.

An Int32 that specifies the maximum number of barcodes to return. Must be a value greater than or equal to 0. The value of 0 means all barcodes.

An array of BarcodeSymbology enumeration members that specifies the barcode symbologies (types) to search for.

An array of BarcodeReadOptions that specifies the options to use. This can be null (Nothing in VB), where the current default options is used. Otherwise, the method will use the options that corresponds to the symbologies being read, if the array does not contain specific options for a symbologies being read, then the default version will be used.

Return Value

An array of BarcodeData objects or derived classes that contains the symbology, data, location and any rotation angle for each barcode found. If no barcodes can be found, then this method will return an empty array (Length equals to 0).


Use this method if you want to read multiple barcodes of the same or multiple symbologies from an image. For example, to read all UPC and QR barcodes in the image, use an array of BarcodeSymbology.UPC-A, BarcodeSymbology.UPC-E and BarcodeSymbology.QR.

LEADTOOLS barcode read engine is optimized for speed and can search for multiple similar symbologies at the same time. This method simply returns the first barcode that is detected correctly using the symbologies and current options.

The ReadSymbology event will occur before and after attempting to read any symbology. The read options being used whether the default or specified will be set in the BarcodeReadSymbologyEventArgs.Options property of the event data.

If  symbologies is null (Nothing in VB), then this method will use all the currently available symbologies. If this parameter contains an empty array, then no barcode will be detected and an empty array will be returned.

The BarcodeReader provides the following barcode read methods:

Method Description
ReadBarcode(RasterImage image, LeadRect searchBounds, BarcodeSymbology symbology) and ReadBarcode(RasterImage image, LeadRect searchBounds, BarcodeSymbology symbology, BarcodeReadOptions options)

Read one barcode from an image with specified symbology and default or specific options. Use these methods if you want to read a single barcode from the image, for example, a QR symbol by specifying BarcodeSymbology.QR or if you want to read any barcode found regardless of its type by using BarcodeSymbology.Unknown.

ReadBarcode(RasterImage image, LeadRect searchBounds, BarcodeSymbology[] symbologies) and ReadBarcode(RasterImage image, LeadRect searchBounds, BarcodeSymbology[] symbologies, BarcodeReadOptions[] options)

Read one barcode from an image with a symbology from a specified group and default or specific options. Use these methods if you want to read a single barcode from a known group. For example, to read a barcode that can be of any UPC type, pass an array of BarcodeSymbology.UPCA and BarcodeSymbology.UPCE.

ReadBarcodes(RasterImage image, LeadRect searchBounds, int maximumBarcodes, BarcodeSymbology[] symbologies) and ReadBarcodes(RasterImage image, LeadRect searchBounds, int maximumBarcodes, BarcodeSymbology[] symbologies, BarcodeReadOptions[] options)

Read multiple barcodes from an image with symbologies from a specified group and default or specific options. Use these methods if you want to read multiple barcodes of the same or multiple symbologies.


This example creates two threads: One for reading horizontal barcodes and one for reading vertical barcodes. Then it uses the same BarcodeReader to try and read all the barcodes from an image using both threads

using Leadtools; 
using Leadtools.Codecs; 
using Leadtools.Barcode; 
using Leadtools.ImageProcessing; 
// This class holds the data we will pass to each thread 
public class MyThreadData 
   // This worker thread name 
   public string Name; 
   // Barcode reader instance 
   public BarcodeReader BarcodeReaderInstance; 
   // Array of options to use 
   public BarcodeReadOptions[] ReadOptions; 
   // Image file containing the barcodes 
   public string ImageFileName; 
   // This will hold the barcodes found 
   public BarcodeData[] Barcodes; 
   // In case of errors 
   public Exception Error; 
   // Event to notify when the thread is finished 
   public ManualResetEvent FinishedEvent; 
public void BarcodeReader_ReadBarcodeExample6() 
   string[] imageFileNames = PrepareImages(); 
   // Create a Barcode engine 
   BarcodeEngine engine = new BarcodeEngine(); 
   // Get the Barcode reader instance 
   BarcodeReader reader = engine.Reader; 
   // Get a version of all read options that support rotated barcodes 
   BarcodeReadOptions[] verticalBarcodeReadOptions = GetVerticalReadBarcodeOptions(reader); 
   // Synchronization events 
   ManualResetEvent[] finishedEvents = new ManualResetEvent[2]; 
   // Create the thread data objects 
   MyThreadData[] threadsData = new MyThreadData[2]; 
   for (int i = 0; i < threadsData.Length; i++) 
      finishedEvents[i] = new ManualResetEvent(false); 
      threadsData[i] = new MyThreadData(); 
      threadsData[i].BarcodeReaderInstance = reader; 
      threadsData[i].ReadOptions = null; 
      threadsData[i].FinishedEvent = finishedEvents[i]; 
   // Setup the read options for the two threads 
   threadsData[0].Name = "Read Default Options Thread"; 
   threadsData[0].ReadOptions = null;  // Default, or horizontal 
   threadsData[1].Name = "Read Vertical Barcodes Thread"; 
   threadsData[1].ReadOptions = verticalBarcodeReadOptions; 
   List<BarcodeData> totalBarcodes = new List<BarcodeData>(); 
   // Now loop through all the images and try to read the barcodes with both threads at the same time 
   foreach (string imageFileName in imageFileNames) 
      Console.WriteLine("Reading barcodes from {0}", imageFileName); 
      for (int i = 0; i < 2; i++) 
         // Clear the previous results (if any), set up the file name and run 
         threadsData[i].Barcodes = null; 
         threadsData[i].Error = null; 
         threadsData[i].ImageFileName = imageFileName; 
         ThreadPool.QueueUserWorkItem(new WaitCallback(ReadBarcodesInThread), threadsData[i]); 
      // Wait till all the threads finishes 
      foreach (ManualResetEvent waitHandle in finishedEvents) 
      // Add the barcodes found to our list 
      for (int i = 0; i < 2; i++) 
         if (threadsData[i].Error != null) 
            Console.WriteLine("{0} had error {1}", threadsData[i].Name, threadsData[i].Error); 
         else if (threadsData[i].Barcodes != null) 
   // We are done, show the total number of barcodes read 
   Console.WriteLine("Done. Total barcodes read: {0}", totalBarcodes.Count); 
private static void ReadBarcodesInThread(object state) 
   MyThreadData threadData = state as MyThreadData; 
   Console.WriteLine("{0} is reading the barcodes", threadData.Name); 
      // Load the image 
      using (RasterCodecs codecs = new RasterCodecs()) 
         using (RasterImage image = codecs.Load(threadData.ImageFileName, 0, CodecsLoadByteOrder.BgrOrGray, 1, 1)) 
            // Read the barcodes using our options 
            threadData.Barcodes = threadData.BarcodeReaderInstance.ReadBarcodes(image, LeadRect.Empty, 0, null, threadData.ReadOptions); 
      Console.WriteLine("{0} has read {1} barcodes", threadData.Name, threadData.Barcodes.Length); 
   catch (Exception ex) 
      // Return the error to main 
      threadData.Error = ex; 
      // Tell main we are done 
private static string[] PrepareImages() 
   // Create a 90 degrees rotated version of Barcode1.tif 
   string originalImageFileName = Path.Combine(LEAD_VARS.ImagesDir, "Barcode1.tif"); 
   string rotatedImageFileName = Path.Combine(LEAD_VARS.ImagesDir, "Barcode1_Rotated90.tif"); 
   using (RasterCodecs codecs = new RasterCodecs()) 
      using (RasterImage image = codecs.Load(originalImageFileName, 0, CodecsLoadByteOrder.BgrOrGray, 1, 1)) 
         RotateCommand rotate = new RotateCommand(90 * 100, RotateCommandFlags.Resize, RasterColor.FromKnownColor(RasterKnownColor.White)); 
         codecs.Save(image, rotatedImageFileName, RasterImageFormat.CcittGroup4, 1); 
   return new string[] { originalImageFileName, rotatedImageFileName }; 
private static BarcodeReadOptions[] GetVerticalReadBarcodeOptions(BarcodeReader reader) 
   // By default, the options read horizontal barcodes only, create an array of options capable of reading vertical barcodes 
   // Notice, we cloned the default options in reader so we will not change the original options 
   OneDBarcodeReadOptions oneDReadOptions = reader.GetDefaultOptions(BarcodeSymbology.UPCA).Clone() as OneDBarcodeReadOptions; 
   oneDReadOptions.SearchDirection = BarcodeSearchDirection.Vertical; 
   FourStateBarcodeReadOptions fourStateReadOptions = reader.GetDefaultOptions(BarcodeSymbology.USPS4State).Clone() as FourStateBarcodeReadOptions; 
   fourStateReadOptions.SearchDirection = BarcodeSearchDirection.Vertical; 
   PostNetPlanetBarcodeReadOptions postNetPlanetReadOptions = reader.GetDefaultOptions(BarcodeSymbology.PostNet).Clone() as PostNetPlanetBarcodeReadOptions; 
   postNetPlanetReadOptions.SearchDirection = BarcodeSearchDirection.Vertical; 
   GS1DatabarStackedBarcodeReadOptions gs1StackedReadOptions = reader.GetDefaultOptions(BarcodeSymbology.GS1DatabarStacked).Clone() as GS1DatabarStackedBarcodeReadOptions; 
   gs1StackedReadOptions.SearchDirection = BarcodeSearchDirection.Vertical; 
   PatchCodeBarcodeReadOptions patchCodeReadOptions = reader.GetDefaultOptions(BarcodeSymbology.PatchCode).Clone() as PatchCodeBarcodeReadOptions; 
   patchCodeReadOptions.SearchDirection = BarcodeSearchDirection.Vertical; 
   PDF417BarcodeReadOptions pdf417ReadOptions = reader.GetDefaultOptions(BarcodeSymbology.PDF417).Clone() as PDF417BarcodeReadOptions; 
   pdf417ReadOptions.SearchDirection = BarcodeSearchDirection.Vertical; 
   MicroPDF417BarcodeReadOptions microPdf417ReadOptions = reader.GetDefaultOptions(BarcodeSymbology.MicroPDF417).Clone() as MicroPDF417BarcodeReadOptions; 
   microPdf417ReadOptions.SearchDirection = BarcodeSearchDirection.Vertical; 
   // Even though this array will not contain all options, it should be enough to read all barcodes, since the version of ReadBarcodes we will use 
   // will use the default options if an overridden is not passed 
   BarcodeReadOptions[] readOptions = 
   oneDReadOptions, fourStateReadOptions, postNetPlanetReadOptions, gs1StackedReadOptions, patchCodeReadOptions, pdf417ReadOptions, microPdf417ReadOptions 
   return readOptions; 
static class LEAD_VARS 
   public const string ImagesDir = @"C:\LEADTOOLS22\Resources\Images"; 

Target Platforms

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Leadtools.Barcode Assembly

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