Qt: resizing a QLabel containing a QPixmap while keeping its aspect ratio

Question

I use a QLabel to display the content of a bigger, dynamically changing QPixmap to the user. It would be nice to make this label smaller/larger depending on the space availa

Answer 1

In order to change the label size you can select an appropriate size policy for the label like expanding or minimum expanding.

You can scale the pixmap by keeping its aspect ratio every time it changes:

QPixmap p; // load pixmap
// get label dimensions
int w = label->width();
int h = label->height();

// set a scaled pixmap to a w x h window keeping its aspect ratio 
label->setPixmap(p.scaled(w,h,Qt::KeepAspectRatio));

There are two places where you should add this code:

• When the pixmap is updated
• In the resizeEvent of the widget that contains the label