Linux中Qt利用QRencode实现二维码生成

骑猪看日落 2022-05-28 11:47 316阅读 0赞

Linux环境下QT中实现二维码生成有两种方法，这两种方法都需要用到开源的代码--qrencode。

第一种方法是下载qrencode源码后，将其移植到目标板子上，然后在程序中包含其路径进行使用；

第二种方法是将qrencode源码添加到自己的程序中，直接调用使用。本文使用的第二种方法进行生成二维码图片。

qrencode是开源的二维码QR码编码库，主要C语言编写的，这样方便移植到各种平台下。

QR Code码特点如图一所示

![20180404163146171][]

一、相关参数介绍

//相关参数
    /**
     * QRcode class.
     * Symbol data is represented as an array contains width*width uchars.
     * Each uchar represents a module (dot). If the less significant bit of
     * the uchar is 1, the corresponding module is black. The other bits are
     * meaningless for usual applications, but here its specification is described.
     * <pre>
     * MSB 76543210 LSB
     *     |||||||`- 1=black/0=white
     *     ||||||`-- data and ecc code area
     *     |||||`--- format information
     *     ||||`---- version information
     *     |||`----- timing pattern
     *     ||`------ alignment pattern
     *     |`------- finder pattern and separator
     *     `-------- non-data modules (format, timing, etc.)
     * </pre>
     */
    typedef struct {
    	int version;         ///< version of the symbol
    	int width;           ///< width of the symbol
    	unsigned char *data; ///< symbol data
    } QRcode;
    
    /**
     * Level of error correction.
     */
    typedef enum {
    	QR_ECLEVEL_L = 0, ///< lowest
    	QR_ECLEVEL_M,
    	QR_ECLEVEL_Q,
    	QR_ECLEVEL_H      ///< highest
    } QRecLevel;
    
    /**
     * Encoding mode.
     */
    typedef enum {
    	QR_MODE_NUL = -1,  ///< Terminator (NUL character). Internal use only
    	QR_MODE_NUM = 0,   ///< Numeric mode
    	QR_MODE_AN,        ///< Alphabet-numeric mode
    	QR_MODE_8,         ///< 8-bit data mode
    	QR_MODE_KANJI,     ///< Kanji (shift-jis) mode
    	QR_MODE_STRUCTURE, ///< Internal use only
    	QR_MODE_ECI,       ///< ECI mode
    	QR_MODE_FNC1FIRST,  ///< FNC1, first position
    	QR_MODE_FNC1SECOND, ///< FNC1, second position
    } QRencodeMode;
    
    //代码中使用的函数
    /**
     * Free the instance of QRcode class.
     * @param qrcode an instance of QRcode class.
     */
    extern void QRcode_free(QRcode *qrcode);
    
    /**
     * Create a symbol from the string. The library automatically parses the input
     * string and encodes in a QR Code symbol.
     * @warning This function is THREAD UNSAFE when pthread is disabled.
     * @param string input string. It must be NUL terminated.
     * @param version version of the symbol. If 0, the library chooses the minimum
     *                version for the given input data.
     * @param level error correction level.
     * @param hint tell the library how Japanese Kanji characters should be
     *             encoded. If QR_MODE_KANJI is given, the library assumes that the
     *             given string contains Shift-JIS characters and encodes them in
     *             Kanji-mode. If QR_MODE_8 is given, all of non-alphanumerical
     *             characters will be encoded as is. If you want to embed UTF-8
     *             string, choose this. Other mode will cause EINVAL error.
     * @param casesensitive case-sensitive(1) or not(0).
     * @return an instance of QRcode class. The version of the result QRcode may
     *         be larger than the designated version. On error, NULL is returned,
     *         and errno is set to indicate the error. See Exceptions for the
     *         details.
     * @throw EINVAL invalid input object.
     * @throw ENOMEM unable to allocate memory for input objects.
     * @throw ERANGE input data is too large.
     */
    extern QRcode *QRcode_encodeString(const char *string, int version, QRecLevel level, QRencodeMode hint, int casesensitive);

二、准备工作

1、准备好Qt

2、下载qrencode动态库(以Ubuntu为例)，如果需要依赖其他库请先下载其他库

sudo apt-get install libqrencode-dev

3、在Qt的pro文件当中添加动态库链接

LIBS += -lqrencode

三、不说废话了，直接上代码

#ifndef QRCODELABEL_H
    #define QRCODELABEL_H
    
    #include <QLabel>
    #include <QPainter>
    #include <qrencode.h>
    #include <QPaintEvent>
    
    class QRcodeLabel : public QLabel
    {
        Q_OBJECT
    
    public:
        explicit QRcodeLabel(QWidget *parent = Q_NULLPTR);
        ~QRcodeLabel();
    
        void setString(const QString str);
        void setLogo(const QString path);
    
    protected:
        virtual void paintEvent(QPaintEvent *ev);
    
    private:
        QRcode* qrcode;
        QPixmap* image;
        bool logo;
    
    };
    
    #endif // QRCODELABEL_H

#include "QRcodeLabel.h"
    
    QRcodeLabel::QRcodeLabel(QWidget *parent) :
        QLabel(parent)
    {
        qrcode = NULL;
    }
    
    QRcodeLabel::~QRcodeLabel()
    {
        if(qrcode != NULL) {
            QRcode_free(qrcode);
        }
    }
    
    void QRcodeLabel::setString(const QString str)
    {
        if(qrcode != NULL) {
            QRcode_free(qrcode);
        }
        qrcode = QRcode_encodeString(str.toStdString().c_str(), 2, QR_ECLEVEL_H, QR_MODE_8, 1);
        update();
    }
    
    void QRcodeLabel::setLogo(const QString path)
    {
        image = new QPixmap(path);
        logo = true;
        update();
    }
    
    void QRcodeLabel::paintEvent(QPaintEvent *ev)
    {
        Q_UNUSED(ev);
        int width = this->width();
        int height = this->height();
        int qrWidth = qrcode->width > 0 ? qrcode->width : 1 ;
        double scaleX = (double)width / (double)qrWidth ;
        double scaleY = (double)height / (double)qrWidth ;
    
        QPainter painter(this);
        painter.setBrush(Qt::white);
        painter.setPen(Qt::NoPen);
        painter.drawRect(this->rect());
        painter.setBrush(Qt::black);
        for(int y = 0; y < qrWidth; ++y) {
            for(int x = 0; x < qrWidth; ++x) {
                uchar node = qrcode->data[y*qrWidth + x];
                if(node & 0x01) {
                    QRectF rectf(x*scaleX, y*scaleY, scaleX, scaleY);
                    painter.drawRects(&rectf, 1);
                }
            }
        }
    
        if(logo) {
            int logoW = width * 0.2;
            int logoH = height * 0.2;
            QRect rect((width-logoW)/2, (height-logoH)/2, logoW, logoH);
            painter.setPen(QPen(Qt::red, 3));
            painter.drawRect(rect);
            painter.drawPixmap(rect, image->copy());
            logo = false;
        }
    }

[20180404163146171]: /images/20220528/597893f6a7a042148666c9cf14da6507.png