Two-dimensional code "immortal" - teach you to make two-dimensional code, read two-dimensional code

We drop the effect:

 QR codes can be seen everywhere now, which greatly facilitates our life, but are you curious about it?

In fact, we can also make a simple QR code. Before we start making it, we need to add a background.

Any computer information is actually composed of a series of 0/1 numbers.

Therefore, based on this, our general idea has been completed: convert all the information into binary codes, then define 0 as black and 1 as white, and draw a solid cube to form our QR code as a whole.

1. Convert binary method

We need to understand that the binary code

     //将字符串信息转化为二进制码，存在 int数组里
     public void change() {
        //存储单个字符的字符串
        String solo = new String();
        //读取整个字符串
        for (int i = 0; i < input.length(); i++) {
            //得到单个字符
            char a = input.charAt(i);
            //将字符转换为二进制码
            int c = (int) a;
            solo = bin(c);
            //让int数组存入,因为我们的得到是字符串，所以需要判断后存入
            //一个字符串存入了16个0/1.
            for (int j = 0; j < 16; j++) {
                if (solo.charAt(j) == '0') {
                    bins.add(0);
                } else {
                    bins.add(1);
                }
            }
        }
        System.out.println(bins);
    }

    //将char转化为二进制码
    public String bin(int a) {
        //存储单个字符的字符串
        String bin = new String();
        //利用位运算，得到最后一位，然后再将数左移一位
        //字符采取的是char类型，一共有16bit，所以字符串要连接16个0/1。
        for (int i = 0; i < 16; i++) {
            //注意二进制码加入位置
            if ((a & 1) == 0) {
                bin = "0" + bin;
            } else {
                bin = "1" + bin;
            }
            a = a >> 1;
        }
        return bin;
    }

2. Drawing method

    //开始绘制
    @Override
    public void paint(Graphics g) {
        super.paint(g);
        //用于使方块间隔
        int wid = 0;
        //用于换行
        int hig = 0;
        //遍历存入所有二进制码的数组
        for (int i = 0; i < bins.size(); i++) {
            if (bins.get(i) == 0) {
                bg.setColor(Color.BLACK);
            } else {
                bg.setColor(Color.WHITE);
            }
            //size为方块尺寸
            bg.fillRect(size * wid, size * hig, size, size);
            wid++;
            //以十六个二进制码为一行，代表一个字符
            if (wid == 16) {
                wid = 0;
                hig++;
            }
        }
        g.drawImage(qrBuff, 200, 350, null);
    }

3. Recognition method (put the QR code in the cached image for recognition)

      public void identify(BufferedImage qrbuff) {
                //存各种颜色int值
                int rgb, red, green, blue, gray;
                //存字符的int值
                int num = 0;
                //存储字符串
                String out = null;
                //为了防止边界干扰，我们将起点放在实心正方形的中心
                for (int j =  size / 2; j < qrbuff.getHeight(); j += size) {
                    for (int i = size / 2; i < qrBuff.getWidth(); i += size) {
                        //因为有时候图片会损失，所以不一定是纯白和纯黑，故我们引进灰度值，更好判断黑白
                        rgb = qrBuff.getRGB(i, j);
                        red = (rgb >> 16) & 255;
                        green = (rgb >> 8) & 255;
                        blue = (rgb >> 0) & 255;
                        gray = (red + green + blue) / 3;
                        if (gray > 127) {
                            //二进制位上为1
                            num = num * 2 + 1;
                        } else {
                            //二进制位上为0
                            num = num *2;
                        }
                    }
                    //防止字符串出现null。
                    //将int转化为所需的char字符，再连接到字符串上
                    if(out == null){
                        out = ""+(char)num;
                    }else {
                        out += (char) num;
                    }
                    num = 0;
                }

4. Interface design

It has been completely rotten, there are only two points worth noting:

1. Using internal listeners can greatly reduce data transfer

        ActionListener ac = new ActionListener() {
            //识别二维码
            @Override
        public void actionPerformed(ActionEvent e) {
            identify(qrBuff);
        }

2. Use a multi-line text edit box:

        JTextArea jt = new JTextArea();
        //设置文本框大小
        jt.setPreferredSize(dim);
        //设置文本框字体
        jt.setFont(new Font("宋体", Font.BOLD,30));
        //设置换行与输出间隔一行
        jt.setLineWrap(true);
        jt.append(out+ "\n");

And that's it! We're done! ! !