Hi all,

we are porting our software to QT. In our software we have a view that shows an image, and the user can drag objects from the toolbar to the page.

The image is always a jpeg, with high resolution, so when we see it on screen is always shrinked. The problem is that the image when shrinked has very poor quality, when comparing to our previous Windows platform using GDI+.

We tried all the render hints available, but the quality is still very poor. I was expecting that for a 3000$ license (not paid, we are testing before), at least the resize algorithms would be some good. In GDI+ we never had to do extra work, just set the render hints, and we get good shrinked image quality!

What do we need to do to have a good shrink image quality?

The JPEG image object is a subclassed QGraphicsRectItem. We tried QImage and QPixmap for drawing the image, but results are the same! The images are drawed inside the paint event in our subclassed QGraphicsRectItem.

void CCanvasPageImage:aint( QPainter *p, const QStyleOptionGraphicsItem *option, QWidget * widget)
{
p->setRenderHints(QPainter::Antialiasing | QPainter::SmoothPixmapTransform | QPainter::TextAntialiasing | QPainter::HighQualityAntialiasing | QPainter::NonCosmeticDefaultPen, true);

p->drawImage( option->exposedRect, m_image, option->exposedRect, Qt::OrderedAlphaDither );
// p->drawPixmap( option->exposedRect, m_pixmap, option->exposedRect );
}

Any help would be appreciatted here...

Thanks