Detailed explanation and analysis of how ZXing-core generates 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"); 
}

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); 
} 
} 
}

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); 
} 
}

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();