[Interest] Scaling out of SVG in QGraphicsScene background
Felix Rubio Dalmau
felix at kngnt.org
Wed Feb 27 07:37:58 CET 2019
Hi Christian,
Thank you for answering. Already tried that, but no luck. Seems as if I have to manually handle the scaling out and low-pass filtering of the image and so.... I do not know, seems weird.
Regards,
Felix
On dimarts, 26 de febrer de 2019 3:00:50 CET Christian Gagneraud wrote:
> On Mon, 25 Feb 2019 at 19:18, Felix Rubio Dalmau via Interest
> <interest at qt-project.org> wrote:
> >
> > Hi all,
> >
> > I am trying to paint a SVG I have on a file on the background of a QGraphicsScene, and I am facing some issues: if I subclass QGraphicsScene and in the __init__ method I add:
> >
> > self.target = QtSvg.QGraphicsSvgItem(target)
> > rect = self.target.boundingRect()
> > self.target.setPos(-rect.width()/2, -rect.height()/2)
> > self.addItem(self.target)
> >
> > So that then in my main window I set the QGraphicsView to do a fitInView (the size of the widget is 500x500), via
> >
> > self.ui.targetView.fitInView(self.scene.sceneRect(), QtCore.Qt.KeepAspectRatio)
> >
> > The result is what expected: a nice, smooth image.
> >
> > However, if I try to draw the SVG on the background of the QGraphicsScene, via:
> >
> > self.renderer = QtSvg.QSvgRenderer(target)
> > rect = self.renderer.defaultSize()
> > self.image = QtGui.QImage(rect, QtGui.QImage.Format_ARGB32)
> > self.painter = QtGui.QPainter(self.image)
> > self.renderer.render(self.painter)
> > self.setBackgroundBrush(QtGui.QBrush(self.image))
> > self.setSceneRect(QtCore.QRectF(QtCore.QPointF(0, 0), QtCore.QSizeF(self.image.size())))
> >
> > Without doing the scaling the picture looks OK, but after doing the scaling the picture looks pixelized. How can I fix that?
> > Also, I have observed that I have to set the scene rectangle, while I understood that the scene itself would take care of that?
>
> Maybe you have a caching issue, see
> https://doc.qt.io/qt-5/qgraphicsview.html#cacheMode-prop
> Maybe as well https://doc.qt.io/qt-5/qgraphicsscene.html#invalidate could help
>
> Chris
>
> >
> > Thank you for your help!
> > Felix
> >
> > PS: for reference, the picture is https://upload.wikimedia.org/wikipedia/commons/1/17/WA_80_cm_archery_target.svg
> >
> >
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> > Interest at qt-project.org
> > https://lists.qt-project.org/listinfo/interest
>
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