QPainter 基础绘图

调用QPainter的接口来绘制一些基本的图形

头文件：

#include <QMainWindow>
#include <QPainter>

namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();

private:
    void paintEvent(QPaintEvent *event);

private:
    Ui::MainWindow *ui;
    int            m_type;
};

源文件：

#include <QRegExp>
#include <QPixmap>
#include "mainwindow.h"
#include "ui_mainwindow.h"

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow),
    m_type(1)
{
    ui->setupUi(this);
}

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

void MainWindow::paintEvent(QPaintEvent *event)
{
    Q_UNUSED(event)
    QPainter painter(this);

    if(m_type == 1) // 绘制文本
    {
        painter.setPen(Qt::blue);
        QFont font;
        font.setFamily("Microsoft YaHei");
        font.setPointSize(50);
        font.setItalic(true);
        font.setBold(true);
        painter.setFont(font);
        painter.drawText(rect(), Qt::AlignCenter, QString::fromLocal8Bit("Qt"));
    }
    else if(m_type == 2) // 绘制直线
    {
        painter.setRenderHint(QPainter::Antialiasing, true);
        painter.setPen(Qt::blue);
        painter.drawLine(QPointF(0, height()), QPointF(width() / 2, height() / 2));
    }
    else if(m_type == 3) // 绘制矩形
    {
        painter.setRenderHint(QPainter::Antialiasing, true);
        painter.setPen(QPen(Qt::blue, 2));
        painter.setBrush(Qt::green);
        painter.drawRect(50, 50, 160, 100);
    }
    else if(m_type == 4) // 绘制弧线
    {
        QRectF rect(90.0, 90.0, 80.0, 90.0);
        int startAngle = 30 * 16;
        int spanAngle = 120 * 16;
        painter.setRenderHint(QPainter::Antialiasing, true);
        painter.setPen(QPen(Qt::blue, 2));
        painter.drawArc(rect, startAngle, spanAngle);

    }
    else if(m_type == 5) // 绘制椭圆，绘制圆
    {
        painter.setRenderHint(QPainter::Antialiasing, true);
        painter.setPen(QPen(Qt::blue, 2));
        painter.drawEllipse(QPointF(120, 160), 50, 20);
        painter.setBrush(Qt::green);
        painter.drawEllipse(QPointF(120, 140), 40, 40);
    }
    else if(m_type == 6) // 绘制多边形
    {
        painter.setRenderHint(QPainter::Antialiasing, true);
        painter.setPen(Qt::blue);
        static const QPointF points[6] = {QPointF(10, 40), QPointF(60, 190), QPointF(110, 160), QPointF(220, 180), QPointF(270, 120), QPointF(220, 280)};
        painter.drawPolygon(points, 6);
    }
    else if(m_type == 7) // 绘制图片
    {
        painter.setRenderHint(QPainter::Antialiasing, true);
        painter.drawPixmap(rect(), QPixmap(":/images/pic.png"));
    }
    else if(m_type == 8) // 绘制圆角矩形
    {
        painter.setRenderHint(QPainter::Antialiasing, true);
        painter.setPen(QPen(Qt::blue,2,Qt::SolidLine));
        painter.drawRoundRect(80,80,210,160,50,50);
    }
    else if(m_type == 9) // 绘制扇形
    {
        painter.setRenderHint(QPainter::Antialiasing, true);
        painter.setPen(QPen(Qt::green,2,Qt::SolidLine));
        painter.drawPie(80,80,210,160,0,500);
    }
    else if(m_type == 10) // 绘制弦
    {
        painter.setRenderHint(QPainter::Antialiasing, true);
        painter.setPen(QPen(Qt::green,2,Qt::SolidLine));
        painter.drawChord(80,80,210,160,500,1000);
    }
}