Qt第十六天’

快来打我* 2022-04-04 03:07 200阅读 0赞

## 坐标变换 ##

**坐标平移  
坐标旋转  
坐标缩放  
状态的保存和恢复**

## widget.h ##

#ifndef WIDGET_H
    #define WIDGET_H
    
    
    #include <QWidget>
    
    
    namespace Ui {
    class Widget;
    }
    
    
    class Widget : public QWidget
    {
    Q_OBJECT
    protected:
        void paintEvent(QPaintEvent *event) Q_DECL_OVERRIDE;
    
    
    public:
    explicit Widget(QWidget *parent = nullptr);
    ~Widget();
    
    
    private:
    Ui::Widget *ui;
    };
    
    
    #endif // WIDGET_H

widget.cpp

#include "widget.h"
    #include "ui_widget.h"
    #include<QPainter>
    #include<stdlib.h>
    #include<math.h>
    #include<iostream>
    
    
    Widget::Widget(QWidget *parent) :
    QWidget(parent),
    ui(new Ui::Widget)
    {
    ui->setupUi(this);
    setPalette(QPalette(Qt::white));
    setAutoFillBackground(true);
    resize(600,500);//初始化窗口大小
    }
    
    
    Widget::~Widget()
    {
    delete ui;
    }
    void Widget::paintEvent(QPaintEvent *event)
    {
        QPainter painter(this);
        painter.setRenderHints(QPainter::Antialiasing|QPainter::TextAntialiasing);//抗锯齿
        //生成五角星顶点坐标，假设原点在五角星中心
        qreal R=100;
        const qreal Pi=3.1415;
        qreal deg=Pi*72/180;
        QPointF points[5]=//将点的坐标设为float型
        {
            QPointF(R,0),
            //需要添加头文件#include<iostream>和#include<math.h>
            QPointF(R*std::cos(deg),-R*std::sin(deg)),
            QPointF(R*std::cos(2*deg),-R*std::sin(2*deg)),
            QPointF(R*std::cos(3*deg),-R*std::sin(3*deg)),
            QPointF(R*std::cos(4*deg),-R*std::sin(4*deg))
        };
        //设置字体
        QFont font;
        font.setPointSize(12);
        font.setBold(true);
        painter.setFont(font);
        //设置画笔
        QPen pen;
        pen.setWidth(2);
        pen.setColor(Qt::black);
        pen.setStyle(Qt::SolidLine);
        pen.setCapStyle(Qt::RoundCap);
        pen.setJoinStyle(Qt::RoundJoin);
        painter.setPen(pen);
        //设置画刷
        QBrush brush;
        brush.setColor(Qt::red);
        brush.setStyle(Qt::Dense1Pattern);
        painter.setBrush(brush);
        //设计绘制五角星的PainterPath
        QPainterPath painterPath;
        painterPath.moveTo(points[0]);
        painterPath.lineTo(points[2]);
        painterPath.lineTo(points[4]);
        painterPath.lineTo(points[1]);
        painterPath.lineTo(points[3]);
        painterPath.closeSubpath();//闭合路径
        //在顶点显示编号
        painterPath.addText(points[0],font,"0");
        painterPath.addText(points[1],font,"1");
        painterPath.addText(points[2],font,"2");
        painterPath.addText(points[3],font,"3");
        painterPath.addText(points[4],font,"4");
        //绘图
        painter.save();//保存坐标
        painter.translate(100,120);//平移
        painter.drawPath(painterPath);//绘图
        painter.drawText(0,0,"S1");//在现在的原点写字
        //painter.restore();//恢复坐标状态
    
    
        painter.resetTransform();//复位坐标变换
        painter.translate(300,120);//平移
        painter.scale(0.8,0.8);//缩小至0.8
        painter.drawPath(painterPath);
        painter.drawText(0,0,"S2");
    
    
        painter.resetTransform();
        painter.translate(500,120);
        painter.rotate(180);//旋转
        painter.drawPath(painterPath);
        painter.drawText(0,0,"S3");
    
    
    /*  for(int i=0;i<30;i++)
        {
            painter.rotate(3);
            painter.drawPath(painterPath);
        }
    */
    }

运行结果  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3RoZVJvb2tpZTE_size_16_color_FFFFFF_t_70]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3RoZVJvb2tpZTE_size_16_color_FFFFFF_t_70]: /images/20220404/df230a92403446b8bd8b368f24386a1e.png