// a.cpp

#include <QGuiApplication>
#include <QImage>
#include <QClipboard>

int main(int argc, char *argv[])
{
    QGuiApplication a(argc, argv);
    QImage image(5000, 5000, QImage::Format_ARGB32);    
    image.fill(Qt::red);
    a.clipboard()->setImage(image);    
    return a.exec();
}

// b.cpp

#include <QGuiApplication> 
#include <QImage> 
#include <QClipboard>

int main(int argc, char *argv[])
{
    QGuiApplication a(argc, argv);
    QClipboard *b = a.clipboard();
    QObject::connect(b, &QClipboard::dataChanged, [b] {
        const QMimeData *data = b->mimeData();
        if (data->hasFormat("image/bmp")) {
            qDebug() << data->data("image/bmp");
        }
    });    
    return a.exec();
}

qt.qpa.xcb: QXcbConnection: XCB error: 16 (BadLength), sequence: 512, resource id: 104857604, major code: 0 (Null), minor code: 0