Qt-interest Archive, August 2007
QPainterPath vs QPixmap speed
Message 1 in thread
Hi...
I have another question for qt-experts regarding qpainterpath:
if I need to show & move a complex path (eg. with more than 5000 items)
along my scene, it's a good idea to draw the painterpath into a pixmap
and then to draw, in the paint event, the pixmap instead of the
painterpath ?
If the painterpath is always the same and does not change or resize,
does this speedup the render process or not ?
If yes, how can render a qpainterpath into a pixmap ? :-)
thanks a lot
Andy
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Message 2 in thread
> if I need to show & move a complex path (eg. with more than 5000
items)
> along my scene, it's a good idea to draw the painterpath into a pixmap
> and then to draw, in the paint event, the pixmap instead of the
> painterpath ?
>
> If the painterpath is always the same and does not change or resize,
> does this speedup the render process or not ?
>
> If yes, how can render a qpainterpath into a pixmap ? :-)
QPainterPath should be able to efficiently handle lots of items (i bet a
lot more than 5000).
Don't try to optimize something that doesn't need optimization ;) You'd
probably make things worse rather than better. (Not to mention the
problems you get into if you want to zoom etc.)
Cheers,
Peter
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Message 3 in thread
Andy Hirsh schrieb:
> Hi...
> ...
> If the painterpath is always the same and does not change or resize,
> does this speedup the render process or not ?
I would expect that drawing a pixmap is always faster than drawing a
(non-trivial) painter path of the same size (width, height) as the pixmap.
> If yes, how can render a qpainterpath into a pixmap ? :-)
The QPixmap inherits from QPaintDevice. That means you can "paint" into
it with a QPainter as you would into a QWidget or QPrinter.
Cheers, Oliver
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