How to round the corners of a QImage?

[n34rt]

How do I create a QImage with a given corner radius?
Ex:

QImage image = QImage(200, 200, QImage::Format_ARGB32, 20);

[mpergand]

@n34rt
painter.setRenderHint(QPainter::Antialiasing);

[Chris Kawa]

Images are rectangular. It's an array of pixels. Do you mean draw a rounded rectangle and have the corners transparent?
To fill image with transparency see QImage::fill.
To draw a rounded rectangle see QPainter::drawRoundedRect.

[n34rt]

@Chris-Kawa
I tried this, but the image is still being painted outside the rounded rect:

    QPainter painter(this);
    painter.drawImage(0, 0, image().scaled(250, 100, Qt::IgnoreAspectRatio, Qt::SmoothTransformation));
    painter.drawRoundedRect(QRect(0, 0, 250, 100), 20.0, 20.0);

The image is a rectangle i need to round her borders first, dont?

[ChrisW67]

    QImage source(256, 256, QImage::Format_ARGB32);
    source.fill(Qt::blue);

    QImage dest(source.size(), QImage::Format_ARGB32);
    dest.fill(Qt::transparent);

    QPainterPath clipPath;
    clipPath.addRoundedRect(source.rect().adjusted(10, 10, -10, -10), 20, 20);
    
    QPainter p(&dest);
    p.setClipPath(clipPath);
    p.drawImage(0, 0, source);
    p.end();

    dest.save("/tmp/test.png");

[n34rt]

@ChrisW67 the picture borders look jagged, how to apply antialiasing to it?

[mpergand]

@n34rt
painter.setRenderHint(QPainter::Antialiasing);