Change pixel color of QPixmap

[KroMignon]

@Jakob-Clausen Perhaps you should try to force pixel format to what you need:

QPixmap IconWidget::changeColor(QPixmap& pixmap, QColor to, QColor from)
{
    QImage temp = pixmap.toImage();
    
    qDebug() << "Pixel format is:" << temp.pixelFormat();
    
    if(temp.pixelFormat() != QImage::Format_ARGB32)
        temp.convertTo(QImage::Format_ARGB32);
    
    for (int y = 0; y < temp.height(); ++y)
    {
        QRgb* s = reinterpret_cast<QRgb *>(temp.scanLine(y));

        for (int x= 0; x < temp.width(); ++x, ++s)
        {
            QColor color = QColor::fromRgba(*s);
            uint8_t alpha = color.alpha();

            to.setAlpha(alpha);
            from.setAlpha(alpha);

            if (color == from)
               *s = to.rgba();
        }
    }

    return QPixmap::fromImage(temp);
}

[Christian Ehrlicher]

QImage::Format_ARGB32_Premultiplied is not a good idea to do the pixel stuff then... see the docs: https://doc.qt.io/qt-5/qimage.html#Format-enum

[Jakob Clausen]

@KroMignon Thats a good idea. convertTo() is introduced in 5.13. But if I use

temp = temp.convertToFormat(QImage::Format_ARGB32);

Then it seems to work.
Thank you very much.