Qt小玩意儿——变色魔法阵（QPainter的部分应用）

不念不忘少年蓝@ 2022-10-15 11:58 185阅读 0赞

效果如下：  
![在这里插入图片描述][20210525092920743.gif]  
头文件：

#ifndef MAGIC_H
    #define MAGIC_H
    
    #include <QWidget>
    #include <QPaintEvent>
    
    class Magic : public QWidget
    {
        
        Q_OBJECT
    public:
        explicit Magic(QWidget *parent = nullptr);
        ~Magic();
    
    protected:
        QPoint rotatePoint(QPoint center,QPoint p1,qreal angle);
    
        void paintEvent(QPaintEvent *event);
        void timerEvent(QTimerEvent *event);
    
        void drawEquilateralTriangle(QPainter &painter,QPoint center,qreal r,qreal angle);
    
    private:
        qreal m_r_1 = 100;
        qreal m_r_2 = 120;
    
        qreal m_angle = 0.0;
        QColor m_color_1 = Qt::red;
        QColor m_color_2 = Qt::blue;
        QColor m_color_3 = Qt::green;
    
        int m_nTimeID = -1;
    };
    
    #endif // MAGIC_H

源文件：

#include "magic.h"
    #include <QPainter>
    #include <QtMath>
    #include <QTimer>
    #include <QDebug>
    
    Magic::Magic(QWidget *parent) : QWidget(parent)
    {
        
    
        this->resize(500,500);
    
       m_nTimeID = this->startTimer(1000/20);
    
    }
    
    Magic::~Magic()
    {
        
        this->killTimer(m_nTimeID);
    }
    
    QPoint Magic::rotatePoint(QPoint center, QPoint p1, qreal angle)
    {
        
        qreal x = center.x() + (p1.x() - center.x()) * qCos(qDegreesToRadians(angle)) -
                (p1.y() - center.y()) * qSin(qDegreesToRadians(angle));
        qreal y = center.y() + (p1.y() - center.y()) * qCos(qDegreesToRadians(angle)) +
                (p1.x() - center.x()) * qSin(qDegreesToRadians(angle));
    
        return QPoint(x,y);
    }
    
    
    void Magic::paintEvent(QPaintEvent *event)
    {
        
        QWidget::paintEvent(event);
    
        QPoint center = QPoint(this->width()/2,this->height()/2);
        QPainter painter(this);
        painter.fillRect(0,0,this->width(),this->height(),QColor(65,65,65)); //背景色
    
        painter.setPen(QPen(m_color_1));
        //绘制第一个三角形
        drawEquilateralTriangle(painter,center,-m_r_1,m_angle);
        //绘制第二个三角形
        drawEquilateralTriangle(painter,center,m_r_1,m_angle);
        //绘制内圆
        painter.setPen(QPen(m_color_2));
        painter.drawEllipse(center.x() - m_r_1,center.y() - m_r_1, m_r_1 * 2,m_r_1 * 2);
        //绘制外圆
        painter.drawEllipse(center.x() - m_r_2,center.y() - m_r_2, m_r_2 * 2,m_r_2 * 2);
        //绘制符咒
        QString texts = QStringLiteral("ⅠMagicⅡMagicⅢMagicⅣMagicⅤMagicⅥMagicⅦMagicⅧMagicⅨMagicⅩ");
        int len = texts.length();
        int i = 0;
        qreal angle = 360.0f / len;
        center += QPoint(-5,5);
        QPoint p1 = center + QPoint(0,-m_r_1 - 10);
    
        painter.setPen(QPen(m_color_3));
        QPoint p2 = p1;
        for(auto s:texts){
        
            painter.save();
            painter.drawText(p2,s);
            i++;
            p2 = rotatePoint(center,p1,angle * i - m_angle);
            painter.restore();
        }
    
    }
    
    void Magic::timerEvent(QTimerEvent *event)
    {
        
        QWidget::timerEvent(event);
    
        m_angle += 10;
        if(m_angle > 360){
        
            m_angle = 0;
        }
    
        m_color_1 = QColor(qrand() % 255,qrand() % 255,qrand() % 255);
        m_color_2 = QColor(qrand() % 255,qrand() % 255,qrand() % 255);
        m_color_3 = QColor(qrand() % 255,qrand() % 255,qrand() % 255);
    
        update();
    }
    
    void Magic::drawEquilateralTriangle(QPainter &painter, QPoint center, qreal r, qreal angle)
    {
        
        QPainterPath triangle;
    
        painter.save();
        QPoint start = QPoint(center.x(),center.y() + r);
        start = rotatePoint(center,start,angle);
        triangle.moveTo(start);
        triangle.lineTo(rotatePoint(center,start,120));
        triangle.lineTo(rotatePoint(center,start,-120));
        triangle.lineTo(start);
        painter.drawPath(triangle);
        painter.restore();
    }

[20210525092920743.gif]: /images/20221014/22ad4a9c2a91433b82a09a5eda98f285.png