Drawing over an image displayed on a QLabel

[franco.amato]

Good morning to all,
I'm developing a camera viewer displaying the camera frames on a QLabel.
I need to draw some circle over the camera frames before display them how can I do?
Best Regards,
Franco

[Lykurg]

Good morning to allWow, there must be a time gap between Italy and Germany...

I guess you get your images from your camera as QPixmap. Then simple create a QPainter and set it to the pixmap and paint on it.
QPainter::QPainter ( QPaintDevice * device )

[franco.amato]

Wow, there must be a time gap between Italy and Germany...
I'm in sud America ;-)


I guess you get your images from your camera as QPixmap. Then simple create a QPainter and set it to the pixmap and paint on it.
I get images from the camera as char aray, then I pack the array into an IplImage (OPenCV) for further processing and then I convert to a QImage to display it.
What I would do is this:
after the processing I convert to a QImage -> at this point I would draw the result of the processing ( some circles ) over the QImage so the user can see it.

Regards,
Franco

[Lykurg]

A QImage is also fine:
QImage img;
QPainter p(&img);
// do your painting using the painter
p.end();

[yakin]

or take a view at the QGraphicsView framework...

Greetz Yakin

[franco.amato]

A QImage is also fine:
QImage img;
QPainter p(&img);
// do your painting using the painter
p.end();


I tried this code as suggested by you:


QImage image = IplImageToQImage( m_resizedImage );

QPainter p(&image);
int rx, ry;
//// processing
p.end();

and I got the following error:
I can not draw on a image with the QImage::Format_Indexed8 format.
How can I do?

Best Regards,
Franco

[Lykurg]

Transform it to a pixmap or to a different format on which you can paint. Sorry but I don't have the time right now to determinate on wich format one can paint. But if you transform better check if a overlay widget is not faster. I assume your images have always the same size, then you should probably better overlay your label with a normal transparent widget and do the painting there.

But do both variant and benchmark them.

[franco.amato]

Transform it to a pixmap or to a different format on which you can paint. Sorry but I don't have the time right now to determinate on wich format one can paint. But if you transform better check if a overlay widget is not faster. I assume your images have always the same size, then you should probably better overlay your label with a normal transparent widget and do the painting there.

But do both variant and benchmark them.

Yes my images have always the same size ( are frames from a video camera ).
So you suggest to me to paint over a widget instead of a QLabel?

regards,
Franco

[Lykurg]

Yes, because a QWidget is lighter then a QLabel. What's about making a complete custom viewer widget?
void Viewer::update(QImage newImage, Foo CircleInformations)
{
m_image = newImage;
m_circles = CircleInformations;
// set size policies of your window according to the image size, of if you sure it will not change then leave it.
update();
}

void Viewer::paintEvent(QPaintEvent *e)
{
QPainter p(this);
p.drawImage(m_image);
// here do your circle painting according to m_circles.
}

[franco.amato]

Hi,
thank you.
Is possible in a QWidget ( or another widget ) to display more than 1 image orizontally?
For example at position 0 I display image_1,
at position ( 0 + width_of_image_1 + 20px ) I display image_2,
at position ( 0 + width_of_image_1 + 20 px + width_of_image_2 + 20 px ) I display image_3?
Best Regards,
Franco

[aamer4yu]

Is possible in a QWidget ( or another widget ) to display more than 1 image orizontally?
Yes,, why not.. its same as fitting three rectangles inside one big rectangle... isnt it :rolleyes: