#include "mainwindow.h"
#include <QApplication>
#include <QPainter>
#include <qpicture.h>
#include <QImage>
int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;
    w.show();
    QPicture pic;
    pic.setBoundingRect(QRect(0,0,500,500));
    QPainter p;
    p.begin(&pic);
    p.setClipRect(0,0,500,500,Qt::ReplaceClip);
    p.fillRect(QRect(0,0,500,500), Qt::red);
    p.end();

    QImage img(500, 500, QImage::Format_ARGB32);
    img.fill(QColor(0,0,0,0));
    p.begin(&img);
    p.setClipRect(100,100,200,200);
    p.drawPicture(0, 0, pic);
    p.end();
    img.save("img.png");
    return a.exec();
}