二维码登录原理及生成与解析

import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.Shape;
import java.awt.geom.RoundRectangle2D;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

import javax.imageio.ImageIO;

import com.swetake.util.Qrcode;

import jp.sourceforge.qrcode.QRCodeDecoder;
import jp.sourceforge.qrcode.exception.DecodingFailedException;  
  
public class TwoDimensionCode {  
    //二维码 SIZE
    private static final int CODE_IMG_SIZE = 235;
    // LOGO SIZE (为了插入图片的完整性，我们选择在最中间插入，而且长宽建议为整个二维码的1/7至1/4)
    private static final int INSERT_IMG_SIZE = CODE_IMG_SIZE/5;
      
    /** 
     * 生成二维码(QRCode)图片 
     * @param content 存储内容 
     * @param imgPath 二维码图片存储路径 
     * @param imgType 图片类型 
     * @param insertImgPath logo图片路径
     */  
    public void encoderQRCode(String content, String imgPath, String imgType, String insertImgPath) {  
        try {  
            BufferedImage bufImg = this.qRCodeCommon(content, imgType, insertImgPath);  
              
            File imgFile = new File(imgPath);
            if (!imgFile.exists())
            {
                imgFile.mkdirs();
            }
            // 生成二维码QRCode图片  
            ImageIO.write(bufImg, imgType, imgFile);  
        } catch (Exception e) {  
            e.printStackTrace();  
        }  
    }   
  
    /** 
     * 生成二维码(QRCode)图片 
     * @param content 存储内容 
     * @param output 输出流 
     * @param imgType 图片类型 
     */  
    public void encoderQRCode(String content, OutputStream output, String imgType) {  
        try {  
            BufferedImage bufImg = this.qRCodeCommon(content, imgType, null);  
            // 生成二维码QRCode图片  
            ImageIO.write(bufImg, imgType, output);  
        } catch (Exception e) {  
            e.printStackTrace();  
        }  
    }  
    
    /**
     * @param content
     * @param imgType
     * @param size
     * @param imgPath    嵌入图片的名称
     * @return
     */
    private BufferedImage qRCodeCommon(String content, String imgType, String imgPath){
        BufferedImage bufImg = null;  
        try {  
            Qrcode qrcodeHandler = new Qrcode();  
            // 设置二维码排错率，可选L(7%)、M(15%)、Q(25%)、H(30%)，排错率越高可存储的信息越少，但对二维码清晰度的要求越小  
            qrcodeHandler.setQrcodeErrorCorrect('M');  
            qrcodeHandler.setQrcodeEncodeMode('B');  
            // 设置设置二维码尺寸，取值范围1-40，值越大尺寸越大，可存储的信息越大  
            qrcodeHandler.setQrcodeVersion(15);  
            // 获得内容的字节数组，设置编码格式  
            byte[] contentBytes = content.getBytes("utf-8");  
            // 图片尺寸  
            int imgSize = CODE_IMG_SIZE;  
            bufImg = new BufferedImage(imgSize, imgSize, BufferedImage.TYPE_INT_RGB);  
            Graphics2D gs = bufImg.createGraphics();  
            // 设置背景颜色  
            gs.setBackground(Color.WHITE);  
            gs.clearRect(0, 0, imgSize, imgSize);  
  
            // 设定图像颜色> BLACK  
            gs.setColor(Color.BLACK);  
            // 设置偏移量，不设置可能导致解析出错  
            final int pixoff = 2;
            final int sz = 3;
            // 输出内容> 二维码  
            if (contentBytes.length > 0 && contentBytes.length < 800) {  
                boolean[][] codeOut = qrcodeHandler.calQrcode(contentBytes);  
                for (int i = 0; i < codeOut.length; i++) {  
                    for (int j = 0; j < codeOut.length; j++) {  
                        if (codeOut[j][i]) {  
                            gs.fillRect(j * sz + pixoff, i * sz + pixoff, sz, sz);  
                        }  
                    }  
                }  
            } else {  
                throw new Exception("QRCode content bytes length = " + contentBytes.length + " not in [0, 800].");  
            }  
            //嵌入logo
            if(imgPath != null)
                this.insertImage(bufImg, imgPath, true);
            gs.dispose();  
            bufImg.flush();  
        } catch (Exception e) {  
            e.printStackTrace();  
        }  
        return bufImg;  
    }
    
    private void insertImage(BufferedImage source, String imgPath,  
            boolean needCompress) throws Exception {  
        File file = new File(imgPath);  
        if (!file.exists()) {  
            System.err.println(""+imgPath+"   该文件不存在！");  
            return;  
        }  
        Image src = ImageIO.read(new File(imgPath));  
        int width = src.getWidth(null);  
        int height = src.getHeight(null);  
        if (needCompress) { // 压缩LOGO  
            if (width > INSERT_IMG_SIZE) {  
                width = INSERT_IMG_SIZE;  
            }  
            if (height > INSERT_IMG_SIZE) {  
                height = INSERT_IMG_SIZE;  
            }  
            Image image = src.getScaledInstance(width, height,  
                    Image.SCALE_SMOOTH);  
            BufferedImage tag = new BufferedImage(width, height,  
                    BufferedImage.TYPE_INT_RGB);  
            Graphics g = tag.getGraphics();  
            g.drawImage(image, 0, 0, null); // 绘制缩小后的图  
            g.dispose();  
            src = image;  
        }  
        // 插入LOGO  
        Graphics2D graph = source.createGraphics();  
        int x = (CODE_IMG_SIZE - width) / 2;  
        int y = (CODE_IMG_SIZE - height) / 2;  
        graph.drawImage(src, x, y, width, height, null);  
        Shape shape = new RoundRectangle2D.Float(x, y, width, width, 6, 6);  
        graph.setStroke(new BasicStroke(3f));  
        graph.draw(shape);  
        graph.dispose();  
    }  
      
    /** 
     * 解析二维码（QRCode） 
     * @param imgPath 图片路径 
     * @return 
     */  
    public String decoderQRCode(String imgPath) {  
        // QRCode 二维码图片的文件  
        File imageFile = new File(imgPath);  
        BufferedImage bufImg = null;  
        String content = null;  
        try {  
            bufImg = ImageIO.read(imageFile);  
            QRCodeDecoder decoder = new QRCodeDecoder();  
            content = new String(decoder.decode(new TwoDimensionCodeImage(bufImg)), "utf-8");   
        } catch (IOException e) {  
            System.out.println("Error: " + e.getMessage());  
            e.printStackTrace();  
        } catch (DecodingFailedException dfe) {  
            System.out.println("Error: " + dfe.getMessage());  
            dfe.printStackTrace();  
        }  
        return content;  
    }  
      
    /** 
     * 解析二维码（QRCode） 
     * @param input 输入流 
     * @return 
     */  
    public String decoderQRCode(InputStream input) {  
        BufferedImage bufImg = null;  
        String content = null;  
        try {  
            bufImg = ImageIO.read(input);  
            QRCodeDecoder decoder = new QRCodeDecoder();  
            content = new String(decoder.decode(new TwoDimensionCodeImage(bufImg)), "utf-8");   
        } catch (IOException e) {  
            System.out.println("Error: " + e.getMessage());  
            e.printStackTrace();  
        } catch (DecodingFailedException dfe) {  
            System.out.println("Error: " + dfe.getMessage());  
            dfe.printStackTrace();  
        }  
        return content;  
    }  
}