I want to place the image in QFrame but the image was drawn by using QPainter so I have to place that image in QFrame please send me the full code for that
What the image was drawn with doesn't matter: you end up with a QImage or a QPixmap, and you will want to put it in a QLabel, not a QFrame. Simply use a QLabel, since it is-a QFrame (and also QWidget and QObject, of course). There's QLabel::setPixmap, and you can easily get a pixmap from a QImage :)
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I would like to draw inside a Qt QFrame, however the QFrame will have a border. As far as I understand, the paintEvent receives a QPainter which is associated to the whole frameRect, so I will have to offset my paint operations of the border. Is this correct? Is there a way of getting a QPainter already associated to the inner part of the widget, without the (variable in size) border?
you have to consider the contentsRect contentsRect()-> Returns the area inside the widget's margins.using the return value rect of contensRect() you can restrict to draw anything inside the rect.
One way to do this would be to embed a QWidget inside the QFrame, place it in a simple QVBoxLayout layout or QStackedLayout layout with no margins and paint the QWidget instead. You'll probably get better performance if you simply offset your painting, though.
In Qt5, I have a QDialog window on which I have drawn a circle as follows:
void MyDialog::paintEvent(QPaintEvent *pe)
{
QPainter painter(this);
painter.setRenderHint(QPainter::Antialiasing,true);
QPen pen(Qt::blue,2);
painter.setPen(pen);
QRect r=QRect(0,0,100,100);
painter.drawEllipse(r);
}
If I draw a larger circle, for example by using QRect(0,0,500,500);, the circle being greater than the dialog window is clipped. So I dragged a QScrollArea onto the the dialog window and decide to draw onto that so that scroll bars are automatically added. The QScrollArea can be accessed using ui->scrollArea.
I changed the above code by setting QPainter painter(ui->scrollArea);. However, nothings appears in the QScrollArea. I read that I need to override the paintEvent of QScrollArea. But I don't know how to do this.
Any help of drawing on the QScrollArea?
Drawing on the QScrollArea is not what you want either because the QScrollArea actually has a viewport widget.
Create another class which inherits QWidget. Override the paintEvent() method and to the painting you mention. Then, add the widget to the scroll area in your dialog.
MyDialog::MyDialog()
{
QScrollArea *pScrl = new QScrollArea(this);
pScrl->setWidget(new MyWidget(pScrl));
... // use a layout to put the scroll area in the dialog
}
To really make it useful you will need to resize the MyWidget instance to the size of the circle that you want to draw.
How to get the font metrics of a QPainter outside paintEvent drawing method? I would need this before painting on the screen.
If you need to do text layout outside of your paint event, just create a QFontMetrics from the font you will be using.
I have a QLabel that I'm constantly setting it's pixmap (video playback). In my application the user needs to be able to draw (boxes) above the video. How can I layer one of the QPaintDevice classes (QWidget, QPixmap, QImage, etc.) directly above and with the same size as the QLabel for painting. This element will need to have a transparent background so shapes drawn on it will appear over the video.
Add the widget you want to draw shapes on as a child widget of the video label. Add a layout first so the child widget will match the size of the parent widget. The code would be something like this:
QHBoxLayout *layout = new QHBoxLayout(videoWidget);
QLabel *overlayWidget = new QLabel();
overlayWidget->setAlignment(Qt::AlignCenter);
overlayWidget->setText("Overlaid Text");
layout->addWidget(overlayWidget);
You should see the text overlaid on the video and it should remain centered over the video widget if it is resized. For your final code, you would use some widget subclass of your own that allowed you to intercept mouse actions and draw rectangles but that's the basic idea.
Is there non-hideous way to resize a QGraphicsView after a call of scale().
My QGraphicsView is embedded in a QScrollArea. When I zoom i want the View the get bigger.
Thx
QGraphicsView itself inherits from QAbstractScrollArea. Embedding it within another QScrollArea would be very strange, and is likely the source of your problems. By default, when you scale a QGraphicsScene larger than the QGraphicsView in which it is displayed, it will show the necessary scroll bars.