Generating and Parsing QR Code Images in Java with ZXing

Today we need to generate QR code images using Java, so we summarize the process.

Goal: Use Google's ZXing Core library to generate and decode QR codes in Java.

Step 1: Add the ZXing Core dependency to the Maven pom.xml:

com.google.zxing
core
3.3.0

Step 2: Import the core classes. The MatrixToImageWriter class provides methods to convert a BitMatrix to a BufferedImage and write it to a file or stream.

import com.google.zxing.common.BitMatrix;

import javax.imageio.ImageIO;
import java.io.File;
import java.io.OutputStream;
import java.io.IOException;
import java.awt.image.BufferedImage;

/**
 *  用于二维码的生成，由Google提供。
 *
 * Created by Eric on 2017/2/15.
 */
public final class MatrixToImageWriter {

    private static final int BLACK = 0xFF000000;
    private static final int WHITE = 0xFFFFFFFF;

    private MatrixToImageWriter() {}

    public static BufferedImage toBufferedImage(BitMatrix matrix) {
        int width = matrix.getWidth();
        int height = matrix.getHeight();
        BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
        for (int x = 0; x < width; x++) {
            for (int y = 0; y < height; y++) {
                image.setRGB(x, y, matrix.get(x, y) ? BLACK : WHITE);
            }
        }
        return image;
    }

    public static void writeToFile(BitMatrix matrix, String format, File file)
            throws IOException {
        BufferedImage image = toBufferedImage(matrix);
        if (!ImageIO.write(image, format, file)) {
            throw new IOException("Could not write an image of format " + format + " to " + file);
        }
    }

    public static void writeToStream(BitMatrix matrix, String format, OutputStream stream)
            throws IOException {
        BufferedImage image = toBufferedImage(matrix);
        if (!ImageIO.write(image, format, stream)) {
            throw new IOException("Could not write an image of format " + format);
        }
    }
}

Step 3: The BufferedImageLuminanceSource class implements LuminanceSource for decoding QR code images.

import com.google.zxing.LuminanceSource;

import java.awt.Graphics2D;
import java.awt.geom.AffineTransform;
import java.awt.image.BufferedImage;

/**
 * 用于二维码的解析，由Google提供。
 *
 * Created by Eric on 2017/2/15.
 */
public final class BufferedImageLuminanceSource extends LuminanceSource {

    private final BufferedImage image;
    private final int left;
    private final int top;

    public BufferedImageLuminanceSource(BufferedImage image) {
        this(image, 0, 0, image.getWidth(), image.getHeight());
    }

    public BufferedImageLuminanceSource(BufferedImage image, int left, int top, int width, int height) {
        super(width, height);

        int sourceWidth = image.getWidth();
        int sourceHeight = image.getHeight();
        if (left + width > sourceWidth || top + height > sourceHeight) {
            throw new IllegalArgumentException("Crop rectangle does not fit within image data.");
        }

        for (int y = top; y < top + height; y++) {
            for (int x = left; x < left + width; x++) {
                if ((image.getRGB(x, y) & 0xFF000000) == 0) {
                    image.setRGB(x, y, 0xFFFFFFFF); // = white
                }
            }
        }

        this.image = new BufferedImage(sourceWidth, sourceHeight, BufferedImage.TYPE_BYTE_GRAY);
        this.image.getGraphics().drawImage(image, 0, 0, null);
        this.left = left;
        this.top = top;
    }

    @Override
    public byte[] getRow(int y, byte[] row) {
        if (y < 0 || y >= getHeight()) {
            throw new IllegalArgumentException("Requested row is outside the image: " + y);
        }
        int width = getWidth();
        if (row == null || row.length < width) {
            row = new byte[width];
        }
        image.getRaster().getDataElements(left, top + y, width, 1, row);
        return row;
    }

    @Override
    public byte[] getMatrix() {
        int width = getWidth();
        int height = getHeight();
        int area = width * height;
        byte[] matrix = new byte[area];
        image.getRaster().getDataElements(left, top, width, height, matrix);
        return matrix;
    }

    @Override
    public boolean isCropSupported() {
        return true;
    }

    @Override
    public LuminanceSource crop(int left, int top, int width, int height) {
        return new BufferedImageLuminanceSource(image, this.left + left, this.top + top, width, height);
    }

    @Override
    public boolean isRotateSupported() {
        return true;
    }

    @Override
    public LuminanceSource rotateCounterClockwise() {
        int sourceWidth = image.getWidth();
        int sourceHeight = image.getHeight();

        AffineTransform transform = new AffineTransform(0.0, -1.0, 1.0, 0.0, 0.0, sourceWidth);

        BufferedImage rotatedImage = new BufferedImage(sourceHeight, sourceWidth, BufferedImage.TYPE_BYTE_GRAY);

        Graphics2D g = rotatedImage.createGraphics();
        g.drawImage(image, transform, null);
        g.dispose();

        int width = getWidth();
        return new BufferedImageLuminanceSource(rotatedImage, top, sourceWidth - (left + width), getHeight(), width);
    }
}

Step 4: Implement a method to generate a QR code image with given text, size, and format.

/**
 *  根据内容，生成指定宽高、指定格式的二维码图片
 *
 * @param text   内容
 * @param width  宽
 * @param height 高
 * @param format 图片格式
 * @return 生成的二维码图片路径
 * @throws Exception
 */
private static String generateQRCode(String text, int width, int height, String format) throws Exception {
    Hashtable
hints = new Hashtable<>();
    hints.put(EncodeHintType.CHARACTER_SET, "utf-8");
    BitMatrix bitMatrix = new MultiFormatWriter().encode(text, BarcodeFormat.QR_CODE, width, height, hints);
    String pathName = "F:/new.png";
    File outputFile = new File(pathName);
    MatrixToImageWriter.writeToFile(bitMatrix, format, outputFile);
    return pathName;
}

Step 5: Provide a helper method to generate a random alphanumeric verification code of a specified length.

/**
 * 随机生成指定长度的验证码
 *
 * @param length 验证码长度
 * @return 生成的验证码
 */
private static String generateNumCode(int length) {
    String val = "";
    String charStr = "char";
    String numStr = "num";
    Random random = new Random();

    //参数length，表示生成几位随机数
    for (int i = 0; i < length; i++) {
        String charOrNum = random.nextInt(2) % 2 == 0 ? charStr : numStr;
        //输出字母还是数字
        if (charStr.equalsIgnoreCase(charOrNum)) {
            //输出是大写字母还是小写字母
            int temp = random.nextInt(2) % 2 == 0 ? 65 : 97;
            val += (char) (random.nextInt(26) + temp);
        } else if (numStr.equalsIgnoreCase(charOrNum)) {
            val += String.valueOf(random.nextInt(10));
        }
    }
    return val;
}

Step 6: Implement a method to parse a QR code image from a file path and return its content.

/**
 * 解析指定路径下的二维码图片
 *
 * @param filePath 二维码图片路径
 * @return
 */
private static String parseQRCode(String filePath) {
    String content = "";
    try {
        File file = new File(filePath);
        BufferedImage image = ImageIO.read(file);
        LuminanceSource source = new BufferedImageLuminanceSource(image);
        Binarizer binarizer = new HybridBinarizer(source);
        BinaryBitmap binaryBitmap = new BinaryBitmap(binarizer);
        Map
hints = new HashMap<>();
        hints.put(DecodeHintType.CHARACTER_SET, "UTF-8");
        MultiFormatReader formatReader = new MultiFormatReader();
        Result result = formatReader.decode(binaryBitmap, hints);

        System.out.println("result 为：" + result.toString());
        System.out.println("resultFormat 为：" + result.getBarcodeFormat());
        System.out.println("resultText 为：" + result.getText());
        //设置返回值
        content = result.getText();
    } catch (Exception e) {
        e.printStackTrace();
    }
    return content;
}

Step 7: Test the generation and parsing in a main class.

import com.google.zxing.*;
import com.google.zxing.common.BitMatrix;
import com.google.zxing.common.HybridBinarizer;

import javax.imageio.ImageIO;
import java.awt.image.BufferedImage;
import java.io.File;
import java.util.HashMap;
import java.util.Hashtable;
import java.util.Map;
import java.util.Random;

/**
 * 利用Google的ZXing工具包，生成和解析二维码图片
 *
* Created by Eric on 2017/2/15.
 */
public class QRCodeEvents {

    public static void main(String[] args) {

        String text = generateNumCode(12);  //随机生成的12位验证码
        System.out.println("随机生成的12位验证码为： " + text);
        int width = 100;    //二维码图片的宽
        int height = 100;   //二维码图片的高
        String format = "png";  //二维码图片的格式

        try {
            //生成二维码图片，并返回图片路径
            String pathName = generateQRCode(text, width, height, format);
            System.out.println("生成二维码的图片路径： " + pathName);

            String content = parseQRCode(pathName);
            System.out.println("解析出二维码的图片的内容为： " + content);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

Note: The example classes omit package statements; add appropriate packages as needed.

Reference: Original article https://www.cnblogs.com/xz-luckydog/p/6402568.html and a promotional note about joining a Java learning QQ group.