利用QT中Qpainter画点，直线，弧线等简单图形

MyImgTest.h:

#ifndef MYIMGTEST_H
#define MYIMGTEST_H
 

#include <QWidget>

class MyImgTest : public QWidget
{
    //Q_OBJECT
public:
    MyImgTest(QWidget* parent = 0);
    ~MyImgTest();
    void paintEvent(QPaintEvent *);
};

#endif

MyImgTest.cpp:

#include "MyImgTest.h"
#include <QPainter>
//#include <QRect>
//#include <QPointF>
//#include <QLineF>

MyImgTest::MyImgTest(QWidget* parent) : QWidget(parent)
{
    setFixedSize(360,360); //固定大小
    setWindowTitle("Hello DevDiv!");
}

MyImgTest::~MyImgTest()
{
   
}

void MyImgTest::paintEvent(QPaintEvent *)
{
    // 画一条直线
    QPainter painter(this);             // 创建QPainter一个对象
    QPen pen;
   
    //pen.setStyle(Qt::DashLine);        
    pen.setColor(Qt::red);           // 设置画笔为黄色
    painter.setPen(pen);                // 设置画笔
    painter.drawLine(rect().topLeft(), rect().bottomRight());

   // 画一个空心矩形
    pen.setColor(Qt::darkRed);
    painter.setPen(pen);
    painter.drawRect(1, 1, 100, 100);     //painter.drawRect(QRect(1, 1, 100, 100));
   
    // 画一个实心矩形
    QBrush bruch(Qt::FDiagPattern);     // 画刷
    painter.setBrush(bruch);            // 设置画刷
    painter.drawRect(QRect(105, 1, 100, 100));
   
   // 画一个多点线
    pen.setColor(Qt::black);
    painter.setPen(pen);
    bruch.setStyle(Qt::NoBrush);        // 将画刷设置成null//fow what
    painter.setBrush(bruch);
    static const QPointF points[4] = {QPointF(210.0, 1), QPointF(220.0, 50.3), QPointF(300, 100.4), QPointF(260.4, 120.0)};
    painter.drawPolyline(points, 4);
   
    // 画多个点
    QPointF pointf[10];
    for (int i=0; i<10; ++i)
    {
        pointf[i].setX(2.0+i*10.0);
        pointf[i].setY(130.0);
    }
    painter.drawPoints(pointf, 10);
   
     // 画多条线
    QLineF linef[5];
    for (int j=0; j<5; ++j)
    {
        linef[j].setP1(QPointF(110.9+j*10, 120.0));
        linef[j].setP2(QPointF(120.8+j*12, 200.0));
    }
    painter.drawLines(linef, 5);
   
    // 画一个多边形
    QPolygonF polygon;
    polygon << QPointF(200.0, 120.0) << QPointF(230.0, 130.0) << QPointF(260.0, 180.0) << QPointF(200.0, 200.0);
    bruch.setStyle(Qt::CrossPattern);
    painter.setBrush(bruch);
    painter.drawPolygon(polygon, Qt::WindingFill);
   
    // 画一个圆角矩形
    QRectF rectangle(290.0, 110.0, 50, 50);
    bruch.setStyle(Qt::SolidPattern);
    painter.setBrush(bruch);
    painter.drawRoundedRect(rectangle, 20.0, 15.0);
   
   // 画一个QString
    painter.drawText(50, 300, "Hello DevDiv!");
 
}
main.cpp：

#include <QApplication>
#include "MyImgTest.h"
int main(int argc,char *argv[])
{
QApplication app(argc,argv);
MyImgTest* widget = new MyImgTest();
    widget->show();
return app.exec();
}
操作步骤：

1.qmake-qt4 -project

2.qmake-qt4

3.make