Painting into QImage with several layer vs one QImage (problem)

Wanderer

Hello

I followed Scrible example (painting into QImage) and it working fine when my brush is transparent. It works expected.
Problem arise when I create another QImage (transparent) and paint into it and then draw both Qimage-s into widget. The "transparent behavior" is different then painting into one QImage, even if this one QImage is transparent.

I wonder where can be problem?

Here is code how I draw two images.

void Little_Painter::paintEvent(QPaintEvent *event)
{
    QPainter painter(this);
    QRect dRect = event->rect();
    painter.drawImage(dRect, m_image, dRect); 
    painter.drawImage(dRect, m_imageDraw, dRect); // m_imageDraw is transparent QImage
}

void Little_Painter::drawLineTo(const QPoint &endPoint)
{
    QPainter painter(&m_imageDraw); // painting into m_imageDraw looks strange with very small transparency
    //QPainter painter(&m_image); // painting into m_image is ok
    painter.setRenderHints(QPainter::Antialiasing | QPainter::SmoothPixmapTransform);
    QRect area;
    m_painterManager.draw(DrawManagerArgs(&painter, &endPoint, &area, &m_lastPoint, &m_measurePoint)); 
    update(area);
    undo_redo_system::setSActive(UndoRedoSpecialActiveArgs(&m_lastPoint));
    m_lastPoint = endPoint;
}

Little_Painter::Little_Painter(QWidget *parent) : QWidget(parent)
  , m_image(parent->size(), QImage::Format_RGBA8888_Premultiplied)
  , m_imageDraw(parent->size(), QImage::Format_RGBA8888_Premultiplied)
// ....

Look at the pictures:

top brush is how brush texture looks like and second two "round paintings" are transparent brush (left set on 2% and right on 1% transparency) and I painted around until I get it non-transparent in the middle.
1. first picture is painting into QImage m_imageDraw
1. picture is painting into QImage m_image without m_imageDraw

picuture: (this looks interesting but it is not intention)
second picture