Composition

[franco.amato]

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]

Did you try it?

[franco.amato]

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]

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]

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]

You can do it many ways. QRubberBand docs has a nice example.

[franco.amato]

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() ) );

rb->setGeometry( QRect( startSelection, QSize() ) );

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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();
}

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();
}

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Where

QPoint startSelection;
QRubberBand* rb;

QPoint startSelection;
QRubberBand* rb;

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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]

Did you initialize rb to 0 in the constructor?

[franco.amato]

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,