QT method for generating QR code pictures

QRCode Introduction to QR code

QR The code is Japan DENSO WAVE INCORPORATED The company in 60 An open two-dimensional code developed in the s , At present, the company has fully disclosed QR Code related standards , If you can't do it, just QR Code related patent rights , And vigorously promote QR Code is used in all walks of life , Even now QR Code has been widely used , Many international standardization organizations incorporate it into the standard . The following is an introduction to the use of in the development process QR Code may involve the main parameters ：

The size of the QR code ：21 Code element ×21 Code element ~177 Code element ×177 Code element （ On each side 4 The symbols are incremented in units ）, The size of the QR code is determined by the version of the code ; The amount of information that a two-dimensional code can contain is related to the size of the code .

QR Code version ：QR Code setting 1 To 40 Different versions of （ species ), Each version has an inherent symbol structure ( Number of symbols ).（ The symbol refers to the composition of QR The square black and white dot of the size .)“ Symbol structure ” It refers to the number of symbols in the two-dimensional code . From version 1(21 Code element ×21 Code element ) Start , In the vertical and horizontal direction respectively with 4 The symbols are incremented in units , Up to the version 40(177 Code element ×177 Code element ).

QR Code error correction level ：QR The code has “ Error correction function ”. Even if the code gets dirty or broken , It can also recover data automatically . this “ Error correction ability ” Have 4 A level ： Level L、 Level M、 Level Q、 Level H, Users can choose the appropriate level according to the use environment .

How to select QR Code version ？

 

How to choose the right QR Code or view QR The specific parameters and introduction of the code can be referred to QR Its official website ：QRcode.com｜DENSO WAVE

The main method

This article mainly explains the use of open source QR code Library in Qt Generate two-dimensional code in the program , We mainly use an open source QR Encoding Library qrencode. We can qrencode Submit to the project for use by adding an external library , Can also be qrencode Add the source code to the project to compile and use , We use the second method , By way of qrencode The source code of is transplanted to our Qt Program to achieve two-dimensional code display .

step

（1） download qrencode Source code

We went to the OpenPKG Project: Download download qrencode Open source program for , What I'm doing is qrencode-4.1.1.tar.gz

qrencode Download at ：OpenPKG Project: Download

(2) take qrencode Transplant the source code to the project

1） Create a new one Qt engineering , take qrencode-4.1.1.tar.gz Unzip all the files in the root directory .c and .h File copy to Qt In Engineering . As shown in the figure ：

2） take qrencode In the source config.h.in Document modified to config.h Join the project , Will just be added to Qt In the project qrenc.c Move the file out of the project , Because this file is the main function of the source code , And Qt Conflicts in , Will cause the program to exit abnormally . After adding, the project looks like this ：

（3） Modify migration file  

1） stay QT Of .pro Add global... To the file Macro definition

DEFINES += HAVE_CONFIG_H

2） stay config.h The document ends with a new definition of macro

#define MAJOR_VERSION 1
#define MICRO_VERSION 1
#define MINOR_VERSION 1
#define VERSION 1

（4） Use

I created an inheritance here QWidget Of Widget main window , stay widget.h Add the following two sentences to the function declaration

void GenerateQRcode(QString tempstr, QLabel *label);
void GenerateQRcode(QString tempstr, QLabel *label, const QString &logo, float scale);

stay widget.c The following program has been added to , These two programs are overloaded functions , It provides an interface for generating and drawing two-dimensional code pictures , The first function is to generate the QR code separately , The second function can add pictures in the middle of the QR code . 

/*trmpst: The information contained in the QR code 
 * label： Display QR code QLabel Control 
 * */
void Widget::GenerateQRcode(QString tempstr, QLabel *label)
{
    QRcode *qrcode; // QR code data 
    // take QString Turn into const char * |2-QR Code version is 2 | QR_ECLEVEL_Q  Fault tolerance level  |QR_MODE_8  Octet data  |1- Case sensitive 
    qrcode = QRcode_encodeString(tempstr.toStdString().c_str(), 2, QR_ECLEVEL_Q, QR_MODE_8, 1);
    qint32 temp_width=label->width(); // Used to display the QR code QLabel size , It is also the size of the QR code image displayed later 
    qint32 temp_height=label->height();
    qint32 qrcode_width = qrcode->width > 0 ? qrcode->width : 1;    // Generated QR code width and height （ The width of the square = Height ）
    double scale_x = (double)temp_width / (double)qrcode_width; // Scale of QR code picture 
    double scale_y =(double) temp_height /(double) qrcode_width;
    QImage mainimg=QImage(temp_width,temp_height,QImage::Format_ARGB32);
    QPainter painter(&mainimg);
    QColor background(Qt::white);
    painter.setBrush(background);
    painter.setPen(Qt::NoPen);
    painter.drawRect(0, 0, temp_width, temp_height);
    QColor foreground(Qt::black);
    painter.setBrush(foreground);
    for( qint32 y = 0; y < qrcode_width; y ++)//qrcode->data Is a saved qrcode_width*qrcode_width A one-dimensional array of data 
    {                                         // Here is to divide this one-dimensional array into each row qrcode_width Data , In the form of a two-dimensional array 
        for(qint32 x = 0; x < qrcode_width; x++)
        {
            unsigned char b = qrcode->data[y * qrcode_width + x];
            if(b & 0x01)
            {// According to the black and white dots in the QR code （1/0）, stay QLabel Draw a two-dimensional code with a zoom ratio on the 
                QRectF r(x * scale_x, y * scale_y, scale_x, scale_y);
                painter.drawRects(&r, 1);
            }
        }
    }
    QPixmap mainmap=QPixmap::fromImage(mainimg);
    label->setPixmap(mainmap);
    label->setVisible(true);
}

/*trmpst: The information contained in the QR code 
 * label： Display QR code QLabel Control 
 * logo： The picture displayed in the middle of the QR code 
 * scale： Zoom ratio of the middle picture 
 * */
void Widget::GenerateQRcode(QString tempstr, QLabel *label, const QString &logo, float scale)
{
    GenerateQRcode(tempstr,  label);
    int width = label->width();
    int height = label->height();
    int logo_width = width *scale;
    int logo_height =  height * scale;
    int logo_x = (width - logo_width) / 2;
    int logo_y = (width - logo_height) / 2;

    const QPixmap *pix = label->pixmap();
    QPixmap temppix(logo);
    QPixmap pix1 = temppix.scaled(QSize(logo_width, logo_height), Qt::KeepAspectRatio);
    QPixmap pix2(width, height);

    QPainter *painter = new QPainter(&pix2);
    QColor background(Qt::white);
    painter->setBrush(background);
    painter->setPen(Qt::NoPen);
    painter->drawRect(0, 0, width, height);
    QColor foreground(Qt::black);
    painter->setBrush(foreground);

    painter->drawPixmap(0,0, width, height, *pix);
    painter->drawPixmap(logo_x,logo_y, logo_width, logo_height, pix1);
    label->setPixmap(pix2);
    delete painter;
}

Take the following procedure as an example

    QLabel *lab1 = new QLabel(this);
    lab1->setGeometry(10,100,200,200);
    QLabel *lab2 = new QLabel(this);
    lab2->setGeometry(300,100,200,200);
    GenerateQRcode("123456789", lab1, ":Imag/jiasu.png",0.2);
    GenerateQRcode("123456789", lab2);

  effect ：

Reference resources ：blog.csdn.net/kangshuaibing/article