Problem applying QGraphicsBlurEffect to a QGraphicsPixmapItem

[ucomesdag]

Hi all,

I try to apply blur to an image but nothing seems to happen and can't wrap my head arround whatmight be wrong here:

QPixmap buffer(image.size());
QGraphicsPixmapItem item(buffer);
QGraphicsBlurEffect effect;
effect.setBlurHints(QGraphicsBlurEffect::QualityHint);
effect.setBlurRadius(5);
item.setGraphicsEffect(&effect);
 
item.pixmap().toImage().save("blur.png");

QPixmap buffer(image.size());
QGraphicsPixmapItem item(buffer);
QGraphicsBlurEffect effect;
effect.setBlurHints(QGraphicsBlurEffect::QualityHint);
effect.setBlurRadius(5);
item.setGraphicsEffect(&effect);

item.pixmap().toImage().save("blur.png");

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[Lykurg]

Ehm, you are constructing an empty pixmap, and blur an empty pixmap results in an empty pixmap You might want to try

QPixmap buffer(image);

QPixmap buffer(image);

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And also I think that the pixmap function of the item returns the unmodified source pixmap of the item. But I am not sure on that. So if you want save it you have to render the scene or set the pixmap to a label and render that back to a pixmap.

[ucomesdag]

Nope it ain't an empty pixmap. But you hit a point, how could I render it as it's offscreen?

[hobbyist]

You will probably have to add your item to a QGraphicsScene, which you can then render() off-screen using your own QPainter. See also QGraphicsView::render() for off-screen rendering and some examples related to printing.