Qt使用随机验证码的实现示例

#ifndef CAPTCHALABEL_H
 
#define CAPTCHALABEL_H
 
#include <QObject>
 
#include <QLabel>
 
class CaptchaLabel : public QLabel
 
{
 
public:
 
    explicit CaptchaLabel(QWidget* parent = nullptr);
 
    //获取随机数
 
    QString getRandNumber() { return m_randNumber; }
 
    void generateRandNumber(int num = 4);  //生成随机数
 
protected:
    void paintEvent(QPaintEvent *event);  //绘制
 
    void mousePressEvent(QMouseEvent *event);  //鼠标按下
 
private:
    QString m_randNumber;  //随机数
 
};
 
#endif // CAPTCHALABEL_H

#include "captchalabel.h"
#include <QDebug>
#include <QRandomGenerator>
#include <QTimer>
#include <QPainter>
#include <QTime>
 
CaptchaLabel::CaptchaLabel(QWidget *parent) : QLabel(parent)
{
    this->setMinimumSize(100, 30);  //设置最小大小
    this->setStyleSheet("background-color:white;");  //白色背景
 
    //随机数种子初始化
    qsrand(QTime(0,0,0).secsTo(QTime::currentTime()));
 
    //生成随机数
    generateRandNumber();
}
 
/**
* @brief CaptchaLabel::generateRandNum 生成随机数，默认是四个数
* @param num
*/
void CaptchaLabel::generateRandNumber(int num)
{
    m_randNumber.clear();
    for(int i = 0; i < num; i++)
    {
        int num = qrand() % 3;
        if(num == 0)  //数字
        {
            m_randNumber += QString::number(qrand()%10);
        }
        else if(num == 1)  //大写字母
        {
            int temp = 'A';
            m_randNumber += static_cast<QChar>(temp + qrand()%26);
        }
        else if(num == 2)  //小写字母
        {
            int temp = 'a';
            m_randNumber += static_cast<QChar>(temp + qrand()%26);
        }
    }
}
 
/**
* @brief CaptchaLabel::paintEvent 绘制验证码
*/
void CaptchaLabel::paintEvent(QPaintEvent *)
{
    QPainter painter(this);
 
    int num = m_randNumber.size();  //几个随机数
    int width = this->width();
    int height = this->height();
 
    //设置字体
    int size = (width/num) < height ? (width/num) : height;
    QFont font;
    font.setPixelSize(size);  //设置字体大小
    font.setItalic(true);  //设置字体倾斜
    font.setFamily(QString("楷体"));
    painter.setFont(font);  //若设置字体加粗，有的随机数会显示不全
 
    QPen pen;
    //绘制随机数
    for(int i = 0; i < num; i++)
    {
        pen = QPen(QColor(qrand()%255, qrand()%255, qrand()%255));
        painter.setPen(pen);
 
        int y = (height-5-size) <= 0 ? 0 : (qrand()%(height-5-size));
        QRectF rect(width/num*i, y, width/num, size);
        //painter.drawRect(rect);  //测试时，查看矩形的位置及大小
        //在矩形rect中绘制大小为size的随机数
        painter.drawText(rect, Qt::AlignHCenter|Qt::AlignBottom, m_randNumber.at(i));
    }
 
    //绘制干扰点
    for(int i = 0; i < (num*25); i++)
    {
        pen = QPen(QColor(qrand()%256, qrand()%256, qrand()%256));
        painter.setPen(pen);
        painter.drawPoint(qrand()%width, qrand()%height);
    }
 
    //绘制干扰线
    for(int i = 0; i < num; i++)
    {
        pen = QPen(QColor(qrand()%256, qrand()%256, qrand()%256));
        painter.setPen(pen);
        painter.drawLine(qrand()%width, qrand()%height, qrand()%width, qrand()%height);
    }
}
 
/**
 
* @brief CaptchaLabel::mousePressEvent 鼠标点击时更换随机数
 
* @param event
 
*/
void CaptchaLabel::mousePressEvent(QMouseEvent *event)
 
{
 
    Q_UNUSED(event);
 
    //重新生成验证码
 
    generateRandNumber();
 
    //实时更新
 
    update();
}