Hello guys I'm drawing 2 lines on top of each other, 1 long and 1 a bit shorter. I draw them on a QGraphicsItem. When I zoom out in my scene, I can see the ovelapping as if the longer line has some opacity, allowing me to see the shorter line below it. But if I zoom back, it looks all good. The color of my line is (180, 180, 180, 255) so no opacity. My line has a width of 1 pixel. My first guess is since 1px at no zoom is 1px, when I zoom out, my 1px becomes less than 1px (problem) but when I zoom in, it becomes more than 1px (so all good). Is there a solution to fix that ? Thx ! :)

Not sure what optimisation flags you are setting on the graphics view but one possibility might be... QGraphicsView::DontAdjustForAntialiasing or render hints set on the graphics view like... QPainter::HighQualityAntialiasing and I guess you read the docs here and here . Remember, all drawing uses the painter in the end unless you are using only OpenGL for your drawing. I hope this helps you find your way to a solution :-)

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painter.drawline() , overlapping opacity problems with 100% opaque pen.

Unsolved General and Desktop

35 Posts 2 Posters 9.6k Views

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kenchan
wrote on last edited by

#25

hello again @Goffer
I tried my test project on Windows and got the same results. It looks like we are stuck with that behaviour.
You could always submit it as a bug.
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Goffer
wrote on last edited by

#26

I ve sent it to the interest mailing list as you suggested. Will see what happens, how could I submit it as a bug ?
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kenchan
wrote on last edited by

#27

You can find out how to do that and much more here
also the wiki is a good place to look around for information.
The developers mailing list is here.

Good luck :-)
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Goffer
wrote on last edited by Goffer

#28

I've submited the bug ticket.
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kenchan
wrote on last edited by

#29

what is the number of the bug report?
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Goffer
wrote on last edited by

#30

https://bugreports.qt.io/browse/QTBUG-63820
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kenchan
wrote on last edited by

#31

OK, got the link and voted for it.
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Goffer
wrote on last edited by

#32

lets see what happens ;)
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Goffer
replied to Goffer on last edited by

#33

@kenchan can you post your C++ example on the bug report ?
thx
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kenchan
wrote on last edited by

#34

OK. I added my comments and zip file to the bug report.
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Goffer
wrote on last edited by

#35

thx ! hoppefully this will help, what do you think of the current "solution" ?
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