main.cpp

#include <QtGui/QGuiApplication>
#include <QApplication>
#include <QMainWindow>
#include <QPainter>
#include <QObject>
#include <QClipboard>

#include <QtGui/QImage>
#include <QtGui/QColor>
#include <QtCore/QStringList>
#include <QtCore/QCommandLineParser>
#include <QPushButton>
#include <QHBoxLayout>
#include <QLabel>
#include <QMessageBox>
#include <iostream>

int main(int argc, char **argv)
{
    QApplication app(argc, argv);
    QMainWindow w;
    QClipboard *clipboard = QGuiApplication::clipboard();

    QPixmap base(500, 500);

    base.fill(Qt::blue);
    QPainter* painter = new QPainter(&base);

    QHBoxLayout *layout = new QHBoxLayout;

    QPushButton *button1 = new QPushButton("Paste clipboard onto image");
    QLabel *label = new QLabel("Image display");

    QObject::connect(
        button1, &QPushButton::clicked,
        [&]( const bool newValue ) { 
            base.fill(Qt::red);
            QPixmap overlay = QPixmap::fromImage(clipboard->image());
            painter->drawPixmap(10, 10, overlay);
            label->setPixmap(base);
            
        }
    );

    label->setPixmap(base);

    layout->addWidget(button1);
    layout->addWidget(label);

    w.setCentralWidget(new QWidget);
    w.centralWidget()->setLayout(layout);

    w.show();
    int returnCode = app.exec();
    return returnCode;
}