How to Resize a QLabel to Maintain the Aspect Ratio of a QPixmap?

Qt: Resizing QLabel to Maintain Aspect Ratio of QPixmap

You seek to display a QPixmap inside a QLabel that adjusts its size while maintaining the original aspect ratio.

Solution:

To achieve this, you can leverage the QSizePolicy and sizeHint() methods without the need for subclassing.

QSizePolicy Adjustment:

Select an appropriate size policy for your QLabel, such as QSizePolicy::Expanding or QSizePolicy::MinimumExpanding. This will allow the label to grow or shrink according to available space.

Preserving Aspect Ratio:

Whenever the QPixmap changes, you can scale it while preserving its aspect ratio:

<code class="cpp">int w = label->width();
int h = label->height();

label->setPixmap(p.scaled(w,h,Qt::KeepAspectRatio));</code>

Event Handling:

Add this code to two key places:

• Pixmap Update: When the QPixmap is dynamically updated.
• ResizeEvent: In the resizeEvent of the widget containing the QLabel. This ensures the label remains properly scaled even when the widget changes size.

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