问启用抗锯齿功能时，为什么会在QGraphicsView中看到像素图切片之间的间隙

EN

class MainWindow : public QWidget
{
    public:
    MainWindow(QWidget *parent = 0);

protected:
    void resizeEvent(QResizeEvent*);

private:
    QGraphicsScene* _scene;
    QGraphicsView* _view;
    qreal _scale;
    static const int _imageWidth = 512;
    static const int _imageHeight = 128;
};

MainWindow::MainWindow(QWidget *parent)
    : QWidget(parent)
{
    _scene = new QGraphicsScene(this);
    _view = new QGraphicsView(_scene, this);

     //this causes gaps to appear ?
    _view->setRenderHints(QPainter::Antialiasing);

    _scene->setBackgroundBrush( QBrush( QColor( Qt::lightGray ) ) );

    QHBoxLayout *layout = new QHBoxLayout(this);
    layout->addWidget(_view);

    setWindowTitle(QString("GapsBetweenTiles- QT Version %1")
       .arg(QT_VERSION_STR));

    QImage img = QImage(_imageWidth, _imageHeight, QImage::Format_RGB32);
    img.fill(QColor(00, 50, 50));

    int offset = 0;
    for (int k=0; k < 10; ++k) {
        QGraphicsPixmapItem* pixitem = _scene->addPixmap( 
                          QPixmap::fromImage(img));
        pixitem->setTransformationMode(Qt::SmoothTransformation);
        pixitem->setPos(0, offset);
        offset += _imageHeight;
    }
    _scale = 1.0;
}

void MainWindow::resizeEvent(QResizeEvent* )
{
    int scaledWidth = (qreal)_view->width() -
                           _view->verticalScrollBar()->width() ;
    qreal scale = (qreal)scaledWidth / (qreal)_imageWidth;
    qreal scaleMult = scale / _scale;

    _view->scale(scaleMult, scaleMult);
    _scale = scale;
}

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;
    w.show();

    return a.exec();
}