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Java QR Code Generator

Generating QR codes in Java is straightforward using a reliable library. This article shows a concise, practical method using ZXing (Zebra Crossing) to create PNG QR codes from text or URLs, plus options for size, error correction, and custom colors.

What you’ll need

• Java 8+ (JDK)
• Maven or Gradle (or add ZXing jars manually)
• ZXing core and javase modules

Maven dependencies:

xml
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<dependency>
<groupId>com.google.zxing</groupId>
  <artifactId>core</artifactId>
  <version>3.5.1</version>
</dependency>
<dependency>
  <groupId>com.google.zxing</groupId>
  <artifactId>javase</artifactId>
  <version>3.5.1</version>
</dependency>

Simple QR code generator (PNG)

This example creates a PNG file from input text, with configurable size and error correction.

java
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import com.google.zxing.*;
import com.google.zxing.client.j2se.MatrixToImageConfig;
import com.google.zxing.client.j2se.MatrixToImageWriter;
import com.google.zxing.common.BitMatrix;
import com.google.zxing.qrcode.decoder.ErrorCorrectionLevel;

import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.HashMap;
import java.util.Map;

public class QRCodeGenerator {
    public static void generate(String text, int size, String filePath) throws Exception {
        Map<EncodeHintType, Object> hints = new HashMap<>();
        hints.put(EncodeHintType.CHARACTER_SET, “UTF-8”);
        hints.put(EncodeHintType.ERROR_CORRECTION, ErrorCorrectionLevel.M); // L, M, Q, H
        hints.put(EncodeHintType.MARGIN, 1);

        BitMatrix bitMatrix = new MultiFormatWriter().encode(
                text,
                BarcodeFormat.QR_CODE,
                size,
                size,
                hints         );

        // Optional: custom colors (foreground, background)
        int foreground = 0xFF000000; // black
        int background = 0xFFFFFFFF; // white
        MatrixToImageConfig config = new MatrixToImageConfig(foreground, background);

        Path path = Paths.get(filePath);
        MatrixToImageWriter.writeToPath(bitMatrix, “PNG”, path, config);
    }

    public static void main(String[] args) throws Exception {
        String text = “https://example.com”;
        int size = 300;
        String filePath = “qrcode.png”;
        generate(text, size, filePath);
        System.out.println(“QR code generated: “ + filePath);
    }
}

Customization options

• Size: change the width/height (e.g., 150–1000 px).
• Error correction: L (7%), M (15%), Q (25%), H (30%) — higher gives more resiliency but larger modules.
• Margin: white border in modules; default often 4; reduce for denser images.
• Colors: set foreground/background in MatrixToImageConfig.
• Encoding: use UTF-8 for non-ASCII text.

Embedding logos

To add a small logo at center:

1. Generate the QR as BufferedImage (MatrixToImageWriter.toBufferedImage).
2. Load logo, scale to ~15–25% of QR size.
3. Draw logo centered using Graphics2D with anti-aliasing.
4. Ensure error correction level is at least Q or H so scanning still works.

Tips for production

• Test with multiple scanner apps/devices.
• For print use higher DPI and larger pixel size.
• Avoid heavy foreground patterns that reduce contrast.
• Use high error correction when embedding logos.
• Cache generated images for repeated requests.

Troubleshooting

• Blank or unreadable QR: increase size, margin, or error correction.
• Non-ASCII text appears wrong: ensure UTF-8 encoding.
• Too dense or scanner fails: reduce data (shorten URL) or increase module size.

Minimal web-service example (Spring Boot)

• Expose an endpoint that returns image/png generated on-the-fly using the same ZXing code and writing to HttpServletResponse output stream.

Quick summary

Use ZXing with proper hints (UTF-8, error correction), choose an appropriate size and margin, and optionally customize colors or embed a logo. Test across devices and increase error correction for logos or damage tolerance.

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