QRDecoder.java

//
// Tries to decode all the files on a certain directory and outputs the result:
// System.out for the files with a qr code
// System.err for the files without a qr code
//
// based on code from https://stackoverflow.com/questions/36210537/find-qr-code-in-image-and-decode-it-using-zxing
//
// needs the ZXing jars from:
// https://oss.sonatype.org/content/repositories/snapshots/com/google/zxing/core/3.3.4-SNAPSHOT/core-3.3.4-20181025.133109-2.jar
// https://oss.sonatype.org/content/repositories/snapshots/com/google/zxing/javase/3.3.4-SNAPSHOT/javase-3.3.4-20181025.133127-2.jar
//
//

//package com.attendance.mark;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;

import java.io.File;

import javax.imageio.ImageIO;

import com.google.zxing.BarcodeFormat;
import com.google.zxing.BinaryBitmap;
import com.google.zxing.EncodeHintType;
import com.google.zxing.MultiFormatReader;
import com.google.zxing.MultiFormatWriter;
import com.google.zxing.NotFoundException;
import com.google.zxing.Result;
import com.google.zxing.WriterException;
import com.google.zxing.client.j2se.BufferedImageLuminanceSource;
import com.google.zxing.client.j2se.MatrixToImageWriter;
import com.google.zxing.common.BitMatrix;
import com.google.zxing.common.HybridBinarizer;
import com.google.zxing.qrcode.decoder.ErrorCorrectionLevel;

public class QRDecoder {

  public static void main(String[] args) throws WriterException, IOException,
      NotFoundException {
    String charset = "UTF-8"; // or "ISO-8859-1"
    Map<EncodeHintType, ErrorCorrectionLevel> hintMap = new HashMap<EncodeHintType, ErrorCorrectionLevel>();
    hintMap.put(EncodeHintType.ERROR_CORRECTION, ErrorCorrectionLevel.L);

    if (args.length == 0) {
      System.err.println("Need a directory path as argument");
      System.exit(1);
    }
    String dirArg = args[0];
    File dir = new File(dirArg);
    File[] directoryListing = dir.listFiles();
    if (directoryListing != null) {
      for (File child : directoryListing) {
        String fname = child.getName();
        if (fname.startsWith("."))
          continue;

        try {
          String filePath = child.getAbsolutePath();
          System.out.println(fname + "\t"
              + readQRCode(filePath, charset, hintMap));
        } catch (NotFoundException e) {
          System.err.println(fname + "\tNo QR found");
        }
      }
    } else {
      System.err.println(dirArg + " is not a directory");
    }


  }

  public static String readQRCode(String filePath, String charset, Map hintMap)
      throws FileNotFoundException, IOException, NotFoundException {
    BinaryBitmap binaryBitmap = new BinaryBitmap(new HybridBinarizer(
        new BufferedImageLuminanceSource(
            ImageIO.read(new FileInputStream(filePath)))));
    Result qrCodeResult = new MultiFormatReader().decode(binaryBitmap);
    return qrCodeResult.getText();
  }
}