EnableDoublePass Property

Summary

Gets or sets a value indicating whether to enable the double pass setting when reading PDF417 symbols.

Syntax

Objective-C

C++/CLI

Java

Python

public bool EnableDoublePass { get; set; }

@property (nonatomic, assign) BOOL enableDoublePass;

public boolean getEnableDoublePass() 
public void setEnableDoublePass(boolean value)

public: 
property bool EnableDoublePass { 
   bool get(); 
   void set (    bool ); 
}

EnableDoublePass # get and set (PDF417BarcodeReadOptions)

Property Value

true to use double pass when reading PDF417 symbols. Otherwise, false. Default value is false.

Remarks

When reading 2D barcodes, LEADTOOLS can perform internal auto pre-processing on the image and try again if the engine cannot detect the required barcode. This may take extra processing and increase the barcode detection time. Therefore, it is best to set EnableDoublePass to true only in certain situations, as follows:

The application is reading barcodes of this type exclusively (for example, a dedicated PDF417 reader is being used). In this case, reading the barcodes is always more important than recognition speed.
The application uses barcode detection on a server. In this case, the time spent on the actual barcode detection is most probably less than the time required to send the image to the server and get the result back due to network latency. Thus it makes sense to enable double pass in this situation.
The images provided have a small resolution (DPI) or are known to come from a source that does not always provide clean images (for example, a Fax machine or a Scanner). Enabling double pass here ensures that the barcodes can be read regardless of the quality of the input image.
The LEADTOOLS .NET C# Barcode demos leave double pass disabled by default. If the engine tries to read a PDF417 barcode but cannot find it, it will then ask the user if DoublePass should be enabled and reading be retried. An approach like that (or an automated one: Read. If failure, enable and read again) can also be used.

Example

Java

using Leadtools; 
using Leadtools.Codecs; 
using Leadtools.Barcode; 
using Leadtools.ImageProcessing; 
 
 
public void PDF417Barcode_Example() 
{ 
   string imageFileName = Path.Combine(LEAD_VARS.ImagesDir, "MyPDF417Barcodes.tif"); 
 
   BarcodeEngine engine = new BarcodeEngine(); 
 
   // Create the image to write the barcodes to 
   int resolution = 300; 
   using (RasterImage image = RasterImage.Create((int)(8.5 * resolution), (int)(11.0 * resolution), 1, resolution, RasterColor.FromKnownColor(RasterKnownColor.White))) 
   { 
      // Write two PDF417 barcodes 
      WriteBarcode(engine.Writer, image, "DATA1", 10, 10, true); 
      WriteBarcode(engine.Writer, image, "DATA2", 20, 20, false); 
 
      // Save the image 
      using (RasterCodecs codecs = new RasterCodecs()) 
      { 
         codecs.Save(image, imageFileName, RasterImageFormat.CcittGroup4, 1); 
      } 
   } 
 
   // Now read the barcodes again 
   using (RasterCodecs codecs = new RasterCodecs()) 
   { 
      using (RasterImage image = codecs.Load(imageFileName)) 
      { 
         ReadBarcodes(engine.Reader, image); 
      } 
   } 
} 
 
private void WriteBarcode(BarcodeWriter writer, RasterImage image, string value, int rows, int columns, bool topLeft) 
{ 
   // Create the barcode data 
   PDF417BarcodeData barcode = new PDF417BarcodeData(); 
   barcode.Value = value; 
   barcode.Group = 0; 
   barcode.Symbology = BarcodeSymbology.PDF417; 
 
   // We will use the alignment to position the barcodes, so use all of the image 
   barcode.Bounds = new LeadRect(0, 0, image.ImageWidth, image.ImageHeight); 
 
   // Set the write options 
   PDF417BarcodeWriteOptions options = new PDF417BarcodeWriteOptions(); 
 
   if (topLeft) 
   { 
      options.HorizontalAlignment = BarcodeAlignment.Near; 
      options.VerticalAlignment = BarcodeAlignment.Near; 
   } 
   else 
   { 
      options.HorizontalAlignment = BarcodeAlignment.Far; 
      options.VerticalAlignment = BarcodeAlignment.Far; 
   } 
 
   options.Truncated = false; 
   options.EnableGroupMode = false; 
   options.SymbolWidthAspectRatio = 2; 
   options.SymbolHeightAspectRatio = 1; 
   options.LimitByRowsAndColumns = true; 
   options.Rows = rows; 
   options.Columns = columns; 
   options.XModule = 30; 
   options.XModuleAspectRatio = 3; 
   options.ECCLevel = PDF417BarcodeECCLevel.Level0; 
   options.ECCPercentage = 0; 
 
   // Write it 
   Console.WriteLine("Writing barcode with symbol rows/columns: {0}/{1} and Data: {2}", rows, columns, value); 
   writer.WriteBarcode(image, barcode, options); 
} 
 
private void ReadBarcodes(BarcodeReader reader, RasterImage image) 
{ 
   // Setup read options 
   PDF417BarcodeReadOptions options = new PDF417BarcodeReadOptions(); 
   options.SearchDirection = BarcodeSearchDirection.Horizontal; 
   options.EnableDoublePass = false; 
   options.EnableFastMode = false; 
   options.ReadMode = PDF417BarcodeReadMode.Mode0; 
   options.ReturnCorruptedSymbolArea = false; 
   options.ReadOptionalMacroFileNameField = false; 
   options.ReadOptionalMacroSegmentCountField = false; 
   options.ReadOptionalMacroTimestampField = false; 
   options.ReadOptionalMacroSenderField = false; 
   options.ReadOptionalMacroAddresseeField = false; 
   options.ReadOptionalMacroFileSizeField = false; 
   options.ReadOptionalMacroChecksumField = false; 
   options.ReadOptionalMacro79AndAZField = false; 
   options.EnableDoublePassIfSuccess = true; 
   options.EnableNoIndicatorTrail = true; 
   options.EnablePreprocessing = true; 
 
   Console.WriteLine("Reading Barcodes"); 
   BarcodeData[] barcodes = reader.ReadBarcodes(image, LeadRect.Empty, 0, new BarcodeSymbology[] { BarcodeSymbology.PDF417 }, new BarcodeReadOptions[] { options }); 
   Console.WriteLine("{0} barcodes found:", barcodes.Length); 
   foreach (PDF417BarcodeData barcode in barcodes) 
   { 
      Console.WriteLine(" At {0} data: {1} and symbology: {2}", barcode.Bounds, barcode.Value, barcode.Symbology); 
   } 
} 
 
static class LEAD_VARS 
{ 
   public const string ImagesDir = @"C:\LEADTOOLS23\Resources\Images"; 
}

 
import static org.junit.Assert.assertTrue; 
 
import java.io.File; 
import java.io.IOException; 
 
import org.junit.*; 
import org.junit.runner.JUnitCore; 
import org.junit.runner.Result; 
import org.junit.runner.notification.Failure; 
 
import leadtools.*; 
import leadtools.barcode.*; 
import leadtools.codecs.*; 
 
 
public void pdf417Barcode_Example() { 
    final String LEAD_VARS_IMAGES_DIR = "C:\\LEADTOOLS23\\Resources\\Images"; 
    String imageFileName = combine(LEAD_VARS_IMAGES_DIR, "MyPDF417Barcodes.tif"); 
    BarcodeEngine engine = new BarcodeEngine(); 
 
    // Create the image to write the barcodes to 
    int resolution = 300; 
    RasterImage image = RasterImage.create((int) (8.5 * resolution), (int) (11.0 * resolution), 1, resolution, 
            RasterColor.fromKnownColor(RasterKnownColor.WHITE)); 
 
    // Write two PDF417 barcodes 
    writeBarcode(engine.getWriter(), image, "DATA1", 10, 10, true); 
    writeBarcode(engine.getWriter(), image, "DATA2", 20, 20, false); 
 
    // Save the image 
    RasterCodecs codecs = new RasterCodecs(); 
    codecs.save(image, imageFileName, RasterImageFormat.CCITT_GROUP4, 1); 
 
    assertTrue("image unsuccessfully saved", new File(imageFileName).exists()); 
    System.out.println("Command run and image saved to " + imageFileName); 
 
    // Now read the barcodes again 
    image = codecs.load(imageFileName); 
    readBarcodes(engine.getReader(), image); 
    image.dispose(); 
    codecs.dispose(); 
} 
 
// Create the barcode data 
private void writeBarcode(BarcodeWriter writer, RasterImage image, String value, int rows, int columns, boolean topLeft) { 
    PDF417BarcodeData barcode = new PDF417BarcodeData(); 
    barcode.setValue(value); 
    barcode.setGroup(0); 
    barcode.setSymbology(BarcodeSymbology.PDF417); 
 
    // We will use the alignment to position the barcodes, so use all of the image 
    barcode.setBounds(new LeadRect(0, 0, image.getImageWidth(), image.getImageHeight())); 
 
    // Set the write options 
    PDF417BarcodeWriteOptions options = new PDF417BarcodeWriteOptions(); 
 
    if (topLeft) { 
        options.setHorizontalAlignment(BarcodeAlignment.NEAR); 
        options.setVerticalAlignment(BarcodeAlignment.NEAR); 
    } else { 
        options.setHorizontalAlignment(BarcodeAlignment.FAR); 
        options.setVerticalAlignment(BarcodeAlignment.FAR); 
    } 
 
    options.setTruncated(false); 
    options.setEnableGroupMode(false); 
    options.setSymbolWidthAspectRatio(2); 
    options.setSymbolHeightAspectRatio(1); 
    options.setLimitByRowsAndColumns(true); 
    options.setRows(rows); 
    options.setColumns(columns); 
    options.setXModule(30); 
    options.setXModuleAspectRatio(3); 
    options.setECCLevel(PDF417BarcodeECCLevel.LEVEL0); 
    options.setECCPercentage(0); 
 
    // Write it 
    System.out.printf("Writing barcode with symbol rows/columns: %1s/%2s and Data: %3s%n", rows, columns, value); 
    writer.writeBarcode(image, barcode, options); 
} 
 
// Setup read options 
private void readBarcodes(BarcodeReader reader, RasterImage image) { 
    PDF417BarcodeReadOptions options = new PDF417BarcodeReadOptions(); 
    options.setSearchDirection(BarcodeSearchDirection.HORIZONTAL); 
    options.setEnableDoublePass(false); 
    options.setEnableFastMode(false); 
    options.setReadMode(PDF417BarcodeReadMode.MODE0); 
    options.setReturnCorruptedSymbolArea(false); 
    options.setReadOptionalMacroFileNameField(false); 
    options.setReadOptionalMacroSegmentCountField(false); 
    options.setReadOptionalMacroTimestampField(false); 
    options.setReadOptionalMacroSenderField(false); 
    options.setReadOptionalMacroAddresseeField(false); 
    options.setReadOptionalMacroFileSizeField(false); 
    options.setReadOptionalMacroChecksumField(false); 
    options.setReadOptionalMacro79AndAZField(false); 
    options.setEnableDoublePassIfSuccess(true); 
    options.setEnablePreprocessing(true); 
 
    System.out.println("Reading Barcodes"); 
    BarcodeData[] barcodes = reader.readBarcodes(image, LeadRect.getEmpty(), 0, 
            new BarcodeSymbology[] { BarcodeSymbology.PDF417 }, new BarcodeReadOptions[] { options }); 
    System.out.printf("%s barcodes found:%n", barcodes.length); 
    for (BarcodeData barcode : barcodes) { 
        System.out.printf(" At %1s data: %2s and symbology: %3s", barcode.getBounds(), barcode.getValue(), 
                barcode.getSymbology()); 
    } 
} 
 
public static String combine(String path1, String path2) { 
    File file = new File(path1, path2); 
    return file.getPath(); 
}

Requirements

Target Platforms

Reference

PDF417BarcodeReadOptions Class

PDF417BarcodeReadOptions Members

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Help Version 23.0.2024.2.29

Leadtools.Barcode Assembly

Introduction

Getting Started

Namespaces

Leadtools.Barcode Namespace

Assemblies