Generating QR Code in Java

The QR code is shortened for Quick Response code. It is an alternative to bar code or we can say that it is a two-dimensional bar-code. It contains the matrix of small squares in which information is stored. It works the same as a bar-code. It can be read by an imaging device. Nowadays, it's being used a lot in every field such as GEO location, on products, vehicle tracking, etc. In this section, we will learn how to generate and read QR code in Java by using the ZXing library.

QR Code

The grid arrangement of the black squares on a white background that can be read by an imaging device is called a QR code. The advantage of a QR code is that it can be scanned by smartphones. We need not to carry any handheld device for scanning. It is used to store information such as text, webpage, URL, etc. It uses the following four standardized encoding modes:

Numeric
Alphanumeric
Byte/binary
Kanji (the Japanese script)

These standard encodings modes store data effectively. The Quick Response system became popular outside the automotive industry due to its fast readability and greater storage capacity compared to standard UPC barcodes.

How does QR code work?

QR code is made up of modules (black and white squares) that contain the encoded data. Modules are arranged in the row and columns that are called Data Matrix. The Placing of data bits starts from the bottom right corner and moves in an upward direction and changes the position while reach at the top.

We scan the QR code through an imaging device such as a camera. After scanning, it processes the QR code using the Reed-Solomon Error Correction Code until the image interpreted. After that, the data is extracted from the patterns that are stored in horizontal and vertical components of the code. The following figure describes the structure of the QR code and its elements.

QR Code Components

There are the two primary components of QR code i.e. Function Patterns and Encoding Regions. These components further divided into small components. The following figure depicts the components of QR code.

The following table describes each component with their work.

Components	Parts of Components	Description
	Quite Zone	It is the boundary of the QR code. The white space around the QR code represents the quiet zone.
Function Patterns	Positioning Patterns	It is also known as finder patterns or position markers. It finds the edges of the QR code.
	Timing Patterns	It helps the scanner to identify the position of rows and columns. The sixth row and column in the QR code are dedicated to the timing pattern.
	Separator	It separates data from the finder pattern.
	Alignment Patterns	It helps the scanner to identify the reference point for alignment.
Encoding Regions	Format Information	It helps the scanner to identify the types of content such as text, URL, etc. It contains data in two parts i.e. Level of Error Correction and masks pattern.
	Version Information	It helps the scanner to identify the version number of the QR code.
	Data Modules	It helps the scanner to decode the data entered by the creator.

Error Correction Levels

A QR code can be scanned even if it is damaged somewhat (up to 30%). The Reed-Solomon Correction algorithm makes it possible. It is to be noted that if we add error correction, it increases the number of the data block in the QR code. So, we need to adjust the level of error correction according to requirements. There are four levels of error correction:

Error Correction Levels and their Capability
Level	Correction in %
Low (L)	7%
Medium (M)	15%
Quartile (Q)	25%
High (H)	30%

The following QR code represents the 7% error correction.

How much data can be stored in the QR code?

The data storage capacity of a QR code depends on the following three:

Datatype (mode or input character set)
Version (1 to 40 different sizes of QR)
Error correction

The version denotes the dimensions of the symbol (i.e. 4 × version number + 17 dots on each side).

Maximum Character Storage Capacity
Encoding mode	Max. characters	Bits/char	Possible characters and default encoding
Numeric only	7,089	31⁄3	0, 1, 2, 3, 4, 5, 6, 7, 8, 9
Alphanumeric	4,296	51⁄2	0-9, A-Z (upper-case only), space, $, %, *, +, -, ., /, :
Binary/byte	2,953	8	ISO 8859-1
Kanji/kana	1,817	13	Shift JIS X 0208

Note: As the version number varies, the number of rows and columns also varies. Therefore, stores the higher information. Also, notable that the QR code contains an equal number of rows and columns. The number of rows and columns depends on the version number.

Generating QR Code

To generate a QR code in Java, we need to use a third-party library named ZXing (Zebra Crossing). It is a popular API that allows us to process with QR code. With the help of the library, we can easily generate and read the QR code. Before moving towards the Java program, we need to add the ZXing library to the project. We can download it from the official site.

After downloading, add it to the classpath. Or add the following dependency in pom.xml file.

<dependencies>
<dependency>
<groupId>com.google.zxing</groupId>
<artifactId>core</artifactId>
<version>3.3.0</version>
</dependency>
<dependency>
<groupId>com.google.zxing</groupId>
<artifactId>javase</artifactId>
<version>3.3.0</version>
</dependency>
</dependencies> 

Let's create a Java program that generates a QR code.

GenerateQrCode.java

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 GenerateQRCode
{
//static function that creates QR Code
public static void generateQRcode(String data, String path, String charset, Map map, int h, int w) throws WriterException, IOException
{
//the BitMatrix class represents the 2D matrix of bits
//MultiFormatWriter is a factory class that finds the appropriate Writer subclass for the BarcodeFormat requested and encodes the barcode with the supplied contents.
BitMatrix matrix = new MultiFormatWriter().encode(new String(data.getBytes(charset), charset), BarcodeFormat.QR_CODE, w, h);
MatrixToImageWriter.writeToFile(matrix, path.substring(path.lastIndexOf('.') + 1), new File(path));
}
//main() method
public static void main(String args[]) throws WriterException, IOException, NotFoundException
{
//data that we want to store in the QR code
String str= "THE HABIT OF PERSISTENCE IS THE HABIT OF VICTORY.";
//path where we want to get QR Code
String path = "C:\\Users\\Anubhav\\Desktop\\QRDemo\\Quote.png";
//Encoding charset to be used
String charset = "UTF-8";
Map<EncodeHintType, ErrorCorrectionLevel> hashMap = new HashMap<EncodeHintType, ErrorCorrectionLevel>();
//generates QR code with Low level(L) error correction capability
hashMap.put(EncodeHintType.ERROR_CORRECTION, ErrorCorrectionLevel.L);
//invoking the user-defined method that creates the QR code
generateQRcode(str, path, charset, hashMap, 200, 200);//increase or decrease height and width accodingly 
//prints if the QR code is generated 
System.out.println("QR Code created successfully.");
}
}

Output:

When we run the above Java program, it generates the following QR code in the specified directory.

Reading QR Code

Let's read the QR code through a Java program that we have generated above.

ReadQrCode.java

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;
import javax.imageio.ImageIO;
import com.google.zxing.BinaryBitmap;
import com.google.zxing.EncodeHintType;
import com.google.zxing.MultiFormatReader;
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.common.HybridBinarizer;
import com.google.zxing.qrcode.decoder.ErrorCorrectionLevel;
public class ReadQRcode 
{
//user-defined method that reads the QR code
public static String readQRcode(String path, String charset, Map map) throws FileNotFoundException, IOException, NotFoundException
{
BinaryBitmap binaryBitmap = new BinaryBitmap(new HybridBinarizer(new BufferedImageLuminanceSource(ImageIO.read(new FileInputStream(path)))));
Result rslt = new MultiFormatReader().decode(binaryBitmap);
return rslt.getText();
}
//main() method
public static void main(String args[]) throws WriterException, IOException, NotFoundException
{
//path where the QR code is saved
String path = "C:\\Users\\Anubhav\\Desktop\\QRDemo\\Quote.png";
//Encoding charset to be used 
String charset = "UTF-8";
Map<EncodeHintType, ErrorCorrectionLevel> hintMap = new HashMap<EncodeHintType, ErrorCorrectionLevel>();
//generates QR code with Low level(L) error correction capability
hintMap.put(EncodeHintType.ERROR_CORRECTION, ErrorCorrectionLevel.L);
System.out.println("Data stored in the QR Code is: \n"+ readQRcode(path, charset, hintMap));
}
}

Output: