View Full Version : Composition
franco.amato
30th November 2009, 20:53
Is still not possible to use composition with a QPixmap in Qt 4..5.3 under windows?
Only QImage?
If not when it will be possible?
Best Regards,
Franco
wysota
30th November 2009, 21:16
Did you try it?
franco.amato
30th November 2009, 21:31
Did you try it?
No, the doc says that. How can I select a region over a Pixmap/Image using composition with the mouse?
Thank you in advance.
Best
wysota
30th November 2009, 22:15
No, the doc says that.
Maybe you should try it?
How can I select a region over a Pixmap/Image using composition with the mouse
Composition is about painting, not selecting things. For painting the selection you can use QPainter::CompositionMode_Xor if you want (or any other composition actually).
franco.amato
30th November 2009, 22:29
Maybe you should try it?
Composition is about painting, not selecting things. For painting the selection you can use QPainter::CompositionMode_Xor if you want (or any other composition actually).
I have to implement the mousePress/Move/ReleaseEvents right? Select a region and paint it?
Or I'm wrong? I have to select a region in the audio waveform .
Can I have a little example with some lines of code?
Best Regards,
Franco
wysota
30th November 2009, 22:38
You can do it many ways. QRubberBand docs has a nice example.
franco.amato
30th November 2009, 23:19
You can do it many ways. QRubberBand docs has a nice example.
dear wysota I tried to implement the rubberBand example but I always get a crash on the line
rb->setGeometry( QRect( startSelection, QSize() ) );
This is mainly my code:
void WaveWidget::mousePressEvent( QMouseEvent* pe )
{
if( pe->button() == Qt::LeftButton )
{
pe->accept();
startSelection = pe->pos();
qDebug() << pe->pos();
if( !rb )
rb = new QRubberBand( QRubberBand::Rectangle, this );
rb->setGeometry( QRect( startSelection, QSize() ) );
rb->show();
}
else
pe->ignore();
}
Where
QPoint startSelection;
QRubberBand* rb;
are private members of my WaveWidget class.
I don't know where my code fails if I exactly copied the code of the doc.
If I comment the setGeometry now it craches on the show method.
Do you have an idea?
Best Regards
wysota
30th November 2009, 23:50
Did you initialize rb to 0 in the constructor?
franco.amato
1st December 2009, 00:52
Did you initialize rb to 0 in the constructor?
No this solved sorry for the trivial error.
A question how can I change the color of the Rubberband region?
Thankx,
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