Detailed explanation and analysis of how ZXing-core generates QR codes

QR codes are everywhere, scan them and you will get gifts. Now that QR codes are so popular, you must not be very clear about how QR codes are generated. Now I will help you learn QR codes by sharing this article with you. How to generate QR code.

In fact, this function is mainly used by using the jar released by goggle.

1. QR code generation

Add the Zxing-core.jar package to the classpath.

The generation of QR code requires the help of the MatrixToImageWriter class, which is provided by Google. You can copy this class into the source code. Here I paste the source code of this class, which can be used directly.

Code that can directly generate QR codes

public void test1() throws Exception{ 
String content = "www.baidu.com"; 
String path = "d://"; 
MultiFormatWriter multiFormatWriter = new MultiFormatWriter();//Zxing是Google提供的关于条码 
Map hints = new HashMap(); 
hints.put(EncodeHintType.CHARACTER_SET, "UTF-8"); 
BitMatrix bitMatrix = multiFormatWriter.encode(content, BarcodeFormat.QR_CODE, 400, 400,hints);//这里是照片的大小 
File file1 = new File(path,"my.jpg"); 
MatrixToImageWriter.writeToFile(bitMatrix, "jpg", file1); 
System.out.println("执行完毕"); 
}

When we can find out, after copying this code, we find that there is a MatrixToImageWriter error, so we need to find it, but I will post the code here, Can be used directly.

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; 
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); 
} 
} 
}

Now you can download the generated QR code from the root directory of the d drive

QR code analysis

Same as generation, we need an auxiliary class (BufferedImageLuminanceSource ), Google also provides this type. Here I also post the source code of this type. You can copy and use it directly, saving you the trouble of searching.

BufferedImageLuminanceSource 
import com.google.zxing.LuminanceSource; 
import java.awt.Graphics2D; 
import java.awt.geom.AffineTransform; 
import java.awt.image.BufferedImage; 
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); 
} 
}

Code for parsing QR codes

MultiFormatReader formatReader = new MultiFormatReader(); 
String filePath = "图片的路径"; 
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(EncodeHintType.CHARACTER_SET, "UTF-8"); 
Result result = formatReader.decode(binaryBitmap,hints); 
System.out.println("result = "+ result.toString()); 
System.out.println("resultFormat = "+ result.getBarcodeFormat()); 
System.out.println("resultText = "+ result.getText()); 
tch (Exception e) { 
e.printStackTrace();

Now you can see the content of the QR code in the console.

The above is the knowledge about ZXing-core’s method of generating QR codes and its analysis introduced by the editor. I hope it will be helpful to you. If you have any questions, please leave me a message. Editor Will reply to everyone promptly. I would also like to thank you all for your support of the PHP Chinese website!

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