Qt第十六天

待我称王封你为后i 2022-04-08 13:24 235阅读 0赞

## QPainter基本绘图 ##

**只有最基本的画图**  
**widget.h**

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

**widget.cpp**

#include "widget.h"
    #include "ui_widget.h"
    
    
    Widget::Widget(QWidget *parent) :
        QWidget(parent),
        ui(new Ui::Widget)
    {
        ui->setupUi(this);
        setPalette(QPalette(Qt::white));//设置背景为白色
        setAutoFillBackground(true);
    }
    
    
    Widget::~Widget()
    {
        delete ui;
    }
    void Widget::paintEvent(QPaintEvent *event)
    {
        QPainter painter(this);
        painter.setRenderHints(QPainter::Antialiasing|QPainter::TextAntialiasing);//反锯齿，文字反锯齿
        int W=this->width();
        int H=this->height();
    /*    //设置区域
        QRect rect1(0,0,W/4,H/4);
        //设置画笔
        QPen pen;
    
    
        pen.setWidth(2);//设置线宽
        pen.setColor(Qt::black);//线色
        pen.setStyle(Qt::SolidLine);//实线线形
        pen.setCapStyle(Qt::FlatCap);//端点样式
        pen.setJoinStyle(Qt::MiterJoin);//连接样式
    
    
        painter.setPen(pen);
        //设置画刷1
        QBrush brush1;
    
    
        brush1.setColor(Qt::green);//颜色
        brush1.setStyle(Qt::HorPattern);//样式
        //QPixmap texturePixmap(":images/images/texture2.jpg");
        //brush.setStyle(Qt::TexturePattern);//材质填充
        //brush.setTexture(texturePixmap);
    
    
        painter.setBrush(brush1);
        //绘图
        painter.drawRect(rect1);
    */
        //渐变效果
        //辐射渐变
    /*  QRadialGradient radiaGrad(W/2,H/2,qMax(W/16,H/16),W/2,H/2);//辐射填充中心（W/2,H/2），辐射填充半径qMax(W/8,H/8)，焦点坐标（W/2,H/2）
        radiaGrad.setColorAt(0,Qt::black);//0是起点
        radiaGrad.setColorAt(1,Qt::white);//1是终点
        radiaGrad.setSpread(QGradient::ReflectSpread);
        painter.setBrush(radiaGrad);
        painter.drawRect(this->rect());//填充更大的区域
    */
        //线形渐变
    /*  QLinearGradient linearGrad(rect().left(),rect().top()/2,rect().right(),rect().top()/2);//
        linearGrad.setColorAt(0,Qt::black);
        linearGrad.setColorAt(0.5,Qt::blue);
        linearGrad.setColorAt(1,Qt::white);
        painter.setBrush(linearGrad);
        painter.drawRect(this->rect());
    */
        //圆锥渐变
    /*  QConicalGradient conicalGrad(W/2,H/2,0);
        conicalGrad.setColorAt(0,Qt::black);
        conicalGrad.setColorAt(0.2,Qt::blue);
        conicalGrad.setColorAt(1,Qt::white);
        painter.setBrush(conicalGrad);
        painter.drawRect(this->rect());
    */
    
    
        QRect rect(W/4,H/4,W/2,H/2);
        int startAngle=90*16;
        int spanAngle=90*16;
        painter.drawArc(rect,startAngle,spanAngle);
        painter.drawChord(rect,startAngle,spanAngle);
        QPoint points[4]={QPoint(5*W/12,H/4),QPoint(3*W/4,5*H/12),QPoint(5*W/12,3*H/4),QPoint(W/4,5*H/12)};
        painter.drawConvexPolygon(points,4);
        QImage image(":images/images/qt.jpg");
        //painter.drawImage(rect,image);
        QVector<QLine>Lines;
        Lines.append(QLine(rect.topLeft(),rect.bottomRight()));
        Lines.append(QLine(rect.topRight(),rect.bottomLeft()));
        Lines.append(QLine(rect.topLeft(),rect.bottomLeft()));
        Lines.append(QLine(rect.topRight(),rect.bottomRight()));
        //painter.drawLines(Lines);
        QPainterPath path;
        path.addEllipse(rect);
        path.addRect(rect);
        painter.fillPath(path,Qt::red);
    }

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/20220405/91bb82c171bb4cc9a4807b17c7d83bf0.png