MikhailS

#include <QMainWindow>
#include <QScrollArea>
#include <QLabel>
#include <QApplication>
#include <QPainter>

class MyLabel : public QLabel {
protected:
	virtual void paintEvent(QPaintEvent* e) {
		QLabel::paintEvent(e);
		
		QPainter p(this);
		
		p.setPen(Qt::green);
		p.drawLine(0, 0, 100, 100);
	}
};

class ImageView : public QMainWindow {
public:
	
	ImageView() : QMainWindow() {
		QScrollArea* scr = new QScrollArea();
		setCentralWidget( scr );
		
		QLabel* label = new MyLabel();
		label->setPixmap(QPixmap("./moon_from_andrey.jpg"));
		scr->setWidget(label);
	}
};


int main(int argc, char* argv[]) {
	QApplication app(argc, argv);
	
	ImageView view;
	view.setGeometry(100, 100, 500, 400);
	view.show();
	
	return app.exec();
}