QImage, possible to change background of resource image (png/jpg)

Question

Can I change the background of a QImage created from a resource (png, jpg) file?

    static QPixmap changeBackground(const QString resource, Qt::GlobalColor color)
    {
        QImage i(resource); // load png/img
        i.fill(color);
        return QPixmap::fromImage(i);
    }

Result of my trial is an all filled with background color image. Any chance that I change the transparent background of the png/jpg resource file?

Can't you just pass QImage::Format_RGB32 to the QImage's ctor? — Garrappachc, Sep 03 '14 at 22:18
You mean to render the transparency invalid? Nice idea, but how could I then set a background color I wish to have? — Horst Walter, Sep 03 '14 at 23:50

score 2 · Accepted Answer · answered Sep 17 '14 at 12:36

How I have done it, improvements are welcome:

QPixmap MyIconClass::changeBackground(const QString resource, Qt::GlobalColor backgroundColor)
{
    QImage resSource(resource);
    QImage destBackground(resSource.size(), QImage::Format_RGB32);
    destBackground.fill(backgroundColor);
    QPainter p(&destBackground);
    p.setCompositionMode(QPainter::CompositionMode_SourceAtop);
    p.drawImage(0, 0, resSource);
    return QPixmap::fromImage(destBackground);
}

QImage, possible to change background of resource image (png/jpg)

1 Answers1