QT5笔记：18 QPainter基本绘图

• 代码

#include "widget.h"
#include "ui_widget.h"

#include <QPainter>

Widget::Widget(QWidget *parent)
    : QWidget(parent)
    , ui(new Ui::Widget)
{
    ui->setupUi(this);
    setPalette(QPalette(Qt::white));
    setAutoFillBackground(true);
}

Widget::~Widget()
{
    delete ui;
}

/**
 * @brief Widget::paintEvent
 * @param event
 * @note 主要画了矩形，折线，图片，文字等，设置画刷、笔、字体等
 */
void Widget::paintEvent(QPaintEvent *event)
{
    Q_UNUSED(event);
    QPainter painter(this);
    int w = this->width();
    int h = this->height();

    //抗锯齿不止这两样，其他请按F1
    painter.setRenderHint(QPainter::Antialiasing);//图像抗锯齿
    painter.setRenderHints(QPainter::TextAntialiasing);//文字抗锯齿

    QPen pen;
    pen.setColor(QColor(90,60,30,128));
    pen.setStyle(Qt::DashDotDotLine);
    pen.setWidth(5);
    pen.setJoinStyle(Qt::BevelJoin);//边角处如何连接，
    painter.setPen(pen);

    QBrush brush;
    brush.setColor(Qt::green);
    brush.setStyle(Qt::CrossPattern);
    painter.setBrush(brush);

    QImage image(":images/main.jpg");

    QFont font;
    font.setPointSize(26);
    font.setBold(true);
    painter.setFont(font);

    QRect rect(w/4,h/4,w/2,h/2);

    QPoint points[] = {QPoint(w/5,h/5), QPoint(w/2,h*4/5), QPoint(w*4/5,h/5)};

    painter.drawRect(rect);
    painter.drawImage(rect,image);
    painter.drawText(rect, Qt::AlignCenter,"Hello, Kitty!");
    pen.setColor(Qt::lightGray);
    painter.setPen(pen);
    painter.drawPolyline(points, sizeof(points)/sizeof (points[0]));
}

• 界面