QTreeWidgetItems, how to make all ttransaprent to see QTreeWidget background

[antartide]

Hello to all, sorry my english =)
My problem is that:
I set a background to my QTreeWidget,
I populate my tree with QTreeWidgetItems and i want to see the background trought the items.
Try with setStyleSheet of the TreeWidget:item : nothing how can i do?
TreeWidget:

void qtg_QTreeWidget::paintEvent(QPaintEvent *event)
{
 
 
        QPainter painter(viewport());
        QImage image("./background.png");
        QRect rect(x(),y(),image.height (),image.width());
        qDebug () <<"paint" << x() << y() << image.height () <<image.width();
        painter.drawImage(rect, image);
        painter.end();
        QTreeWidget::paintEvent(event);
};

void qtg_QTreeWidget::paintEvent(QPaintEvent *event)
{


        QPainter painter(viewport());
        QImage image("./background.png");
        QRect rect(x(),y(),image.height (),image.width());
        qDebug () <<"paint" << x() << y() << image.height () <<image.width();
        painter.drawImage(rect, image);
        painter.end();
        QTreeWidget::paintEvent(event);
};

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TreeWidgetItem

gui_laucher::gui_laucher(QWidget *parent)
    : QWidget(parent)
{
    setupTray();
    int y= m_tray->geometry().y() ;
    int x= m_tray->geometry().x() ;
    setGeometry(x+3,y+3,300,320);
    setAttribute(Qt::WA_TranslucentBackground);
    QStringList labels;
    labels << tr("Software");
 
    m_treeWidget = new qtg_QTreeWidget(this);
    setStyleSheet("QTreeView::item {background-color :rgba(255,255,255,0%);}");
    xmlparser();
}

gui_laucher::gui_laucher(QWidget *parent)
    : QWidget(parent)
{
    setupTray();
    int y= m_tray->geometry().y() ;
    int x= m_tray->geometry().x() ;
    setGeometry(x+3,y+3,300,320);
    setAttribute(Qt::WA_TranslucentBackground);
    QStringList labels;
    labels << tr("Software");

    m_treeWidget = new qtg_QTreeWidget(this);
    setStyleSheet("QTreeView::item {background-color :rgba(255,255,255,0%);}");
    xmlparser();
}

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I also try this:

qtg_QTreeWidgetItem::qtg_QTreeWidgetItem(QTreeWidgetItem *parent) :
    QTreeWidgetItem(parent)
{
    m_pProcessPath="nopath";
    m_pStringParameters="noparams";
 
    setBackground(0,QBrush(Qt::transparent));
}

qtg_QTreeWidgetItem::qtg_QTreeWidgetItem(QTreeWidgetItem *parent) :
    QTreeWidgetItem(parent)
{
    m_pProcessPath="nopath";
    m_pStringParameters="noparams";

    setBackground(0,QBrush(Qt::transparent));
}

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I never can see the picture trought the item =(