How to Resize a QLabel with a QPixmap while Maintaining Aspect Ratio?

Resizing a QLabel with a QPixmap Preserving Aspect Ratio

To display a dynamically changing QPixmap in a QLabel, you may encounter the need to resize the label based on available space while maintaining the QPixmap's aspect ratio. This question aims to address this challenge without resorting to subclassing.

Solution

To achieve this functionality without subclassing, the following approach can be employed:

1. Setting Size Policy: Assign the label an appropriate size policy, such as QSizePolicy::Expanding or QSizePolicy::MinimumExpanding. This allows the label to expand or shrink within its container.

2. Scaling Pixmap Dynamically: To scale the pixmap while preserving its aspect ratio every time it changes, implement the following steps:

   • Obtain the label's current dimensions (width and height).
   • Utilize the QLabel::setPixmap() method with the Qt::KeepAspectRatio scaling option to set a scaled pixmap to the label.

3. Code Placement: This code can be placed in two locations:

   • When the pixmap is updated
   • In the resizeEvent handler of the widget containing the label

By implementing these steps, you can dynamically resize the QLabel while preserving the aspect ratio of its QPixmap, ensuring that the image remains proportional and visually appealing regardless of the available space.

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