How to convert image to qr code using java?-CodePudding

If we search image to qr code, there are many websites which converts image to qr code online.

But how can I do this in java?
I am using the following code for converting text to qr code:-

import java.io.File;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;
import com.google.zxing.BarcodeFormat;
import com.google.zxing.EncodeHintType;
import com.google.zxing.MultiFormatWriter;
import com.google.zxing.NotFoundException;
import com.google.zxing.WriterException;
import com.google.zxing.client.j2se.MatrixToImageWriter;
import com.google.zxing.common.BitMatrix;
import com.google.zxing.qrcode.decoder.ErrorCorrectionLevel;

public class MyQr {

    public static void createQR(String data, String path,
                                String charset, Map hashMap,
                                int height, int width)
        throws WriterException, IOException
    {

        BitMatrix matrix = new MultiFormatWriter().encode(
            new String(data.getBytes(charset), charset),
            BarcodeFormat.QR_CODE, width, height);

        MatrixToImageWriter.writeToFile(
            matrix,
            path.substring(path.lastIndexOf('.')   1),
            new File(path));
    }

    public static void main(String[] args)
        throws WriterException, IOException,
            NotFoundException
    {

        String data = "TEXT IN QR CODE";

        String path = "image.png";
        String charset = "UTF-8";

        Map<EncodeHintType, ErrorCorrectionLevel> hashMap
            = new HashMap<EncodeHintType,
                        ErrorCorrectionLevel>();

        hashMap.put(EncodeHintType.ERROR_CORRECTION,
                    ErrorCorrectionLevel.L);

        createQR(data, path, charset, hashMap, 200, 200);
    }
}

But how to encode a image in qr code?

CodePudding user response：

I assume that you mean that you want to add an image (e.g. logo) to the QR Code.

This is generally done by overlaying a small image on top of the QR Code, usually in the center. QR Codes are still readable when a small portion is obscured, especially in the center.

You can use MatrixToImageWriter.toBufferedImage(matrix) to get a BufferedImage containing the QR Code image, and then use Java image methods to overlay the image. See, for example, overlay images in java

CodePudding user response：

Images are too big to be embedded into QR codes (with the exception of tiny icons). So instead, the image is put on a publicly accessible server and the URL of the image is embedded in the QR code.

Thus you need access to a server that can fulfill this. That's probably the bigger part of what you are about to implement.

Otherwise, it's straight-forward:

import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;
import java.nio.file.Path;
import java.util.HashMap;
import java.util.Map;
import com.google.zxing.BarcodeFormat;
import com.google.zxing.EncodeHintType;
import com.google.zxing.MultiFormatWriter;
import com.google.zxing.WriterException;
import com.google.zxing.client.j2se.MatrixToImageWriter;
import com.google.zxing.common.BitMatrix;
import com.google.zxing.qrcode.decoder.ErrorCorrectionLevel;

public class MyQr {

    /**
     * Uploads the image to a server and returns to image URL.
     * @param imagePath path to the image
     * @return image URL
     */
    public static URL uploadImage(String imagePath)
    {
        // implement a solution to put an image on a public server
        try {
            return new URL("https://yourserver/some_path/image.jpg");
        } catch (MalformedURLException e) {
            throw new RuntimeException(e);
        }
    }

    public static void createQR(String payloadImagePath, String qrCodeImagePath,
                                Map<EncodeHintType, ?> hints, int height, int width)
            throws WriterException, IOException
    {
        URL imageURL = uploadImage(payloadImagePath);

        BitMatrix matrix = new MultiFormatWriter().encode(
                imageURL.toString(), BarcodeFormat.QR_CODE, width, height, hints);

        String imageFormat = qrCodeImagePath.substring(qrCodeImagePath.lastIndexOf('.')   1);
        MatrixToImageWriter.writeToPath(matrix, imageFormat, Path.of(qrCodeImagePath));
    }

    public static void main(String[] args)
            throws WriterException, IOException
    {
        String payloadImagePath = "embed_this.jpg";
        String qrCodeImagePath = "qrcode.png";

        Map<EncodeHintType, ErrorCorrectionLevel> hints = new HashMap<>();
        hints.put(EncodeHintType.ERROR_CORRECTION, ErrorCorrectionLevel.L);

        createQR(payloadImagePath, qrCodeImagePath, hints, 200, 200);
    }
}

BTW: The below code (from your code sample) is non-sense. At best, it creates a copy of the string, which is unnecessary. At worst, it corrupts all characters not supported by charset. I don't think you intended either one.

new String(data.getBytes(charset), charset)