Generating and parsing QR code in Java

Today, I meet the need to use Java to generate two-dimensional code pictures. Let me summarize.

Objective: with the help of ZXing Core toolkit provided by Google, the generation and analysis of two-dimensional code can be realized with Java language.

The steps are as follows:

1. In Maven project, ZXing Core toolkit is introduced into pom.xml:

<!-- https://mvnrepository.com/artifact/com.google.zxing/core -->
        <dependency>
            <groupId>com.google.zxing</groupId>
            <artifactId>core</artifactId>
            <version>3.3.0</version>
        </dependency>

2. First, you need to export the MatrixToImageWriter class provided by Google, which is the core class to generate QR code pictures:

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;

/**
 *  For the generation of QR code, provided by Google.
 *
 * 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);
        }
    }

Thirdly, we need to export the BufferedImageLuminanceSource class provided by Google, which is the core class to realize the resolution of QR code images:

import com.google.zxing.LuminanceSource;

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

/**
 * For QR code parsing, provided by Google.
 *
 * 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);
    }

}

3. Implementation method of generating two-dimensional code picture:

/**
     * Generate a QR code picture of specified width, height and format according to the content
     *
     * @param text   content
     * @param width  wide
     * @param height high
     * @param format Picture format
     * @return Generated QR code picture path
     * @throws Exception
     */
    private static String generateQRCode(String text, int width, int height, String format) throws Exception {
        Hashtable<EncodeHintType, Object> 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;
    }

4. Give a useful small method ----- > randomly generate the verification code of the specified len gt h of alphanumeric combination:

/**
     * Randomly generate verification code of specified length
     *
     * @param length Length of verification code
     * @return Generated verification code
     */
    private static String generateNumCode(int length) {
        String val = "";
        String charStr = "char";
        String numStr = "num";
        Random random = new Random();

        //The parameter length indicates that several random numbers are generated
        for (int i = 0; i < length; i++) {

            String charOrNum = random.nextInt(2) % 2 == 0 ? charStr : numStr;
            //Output letters or numbers
            if (charStr.equalsIgnoreCase(charOrNum)) {
                //Output is upper or lower case
                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;
    }

5. The implementation method of parsing the QR code image under the specified path:

/**
     * Resolve the QR code picture under the specified path
     *
     * @param filePath QR code picture path
     * @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<DecodeHintType, Object> hints = new HashMap<>();
            hints.put(DecodeHintType.CHARACTER_SET, "UTF-8");
            MultiFormatReader formatReader = new MultiFormatReader();
            Result result = formatReader.decode(binaryBitmap, hints);

            System.out.println("result For:" + result.toString());
            System.out.println("resultFormat For:" + result.getBarcodeFormat());
            System.out.println("resultText For:" + result.getText());
            //Set return value
            content = result.getText();
        } catch (Exception e) {
            e.printStackTrace();
        }
        return content;
    }

6. Test classes for QR code generation and analysis:

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;

/**
 * Using Google's ZXing toolkit to generate and analyze QR code images
 * <p>
 * Created by Eric on 2017/2/15.
 */
public class QRCodeEvents {

    public static void main(String[] args) {

        String text = generateNumCode(12);  //Randomly generated 12 bit verification code
        System.out.println("The randomly generated 12 digit verification code is: " + text);
        int width = 100;    //Width of QR code picture
        int height = 100;   //The height of the QR code picture
        String format = "png";  //Format of QR code picture

        try {
            //Generate a QR code picture and return to the picture path
            String pathName = generateQRCode(text, width, height, format);
            System.out.println("Image path to generate QR Code: " + pathName);

            String content = parseQRCode(pathName);
            System.out.println("The content of the picture that parses the QR code is: " + content);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

Note: the package statement is not written in the above class, which needs to be supplemented by yourself.

Tags: Java Google Maven xml

Posted on Mon, 04 May 2020 21:29:37 -0700 by __greg