setting QPixmap's alpha channel

[ugluk]

Does there exist a better way to do it than this?

void setAlphaChannel(QPixmap& pixmap, int const alpha)
{
  QImage image(pixmap.toImage().convertToFormat(QImage::Format_ARGB32));
 
  for (int x(0); x != image.width(); ++x)
  {
    for (int y(0); y != image.height(); ++y)
    {
      QColor color(image.pixel(x,y));
 
      color.setAlpha(alpha);
 
      image.setPixel(x, y, color.rgba());
    }
  }
 
  pixmap = QPixmap::fromImage(image);
}

void setAlphaChannel(QPixmap& pixmap, int const alpha)
{
  QImage image(pixmap.toImage().convertToFormat(QImage::Format_ARGB32));

  for (int x(0); x != image.width(); ++x)
  {
    for (int y(0); y != image.height(); ++y)
    {
      QColor color(image.pixel(x,y));

      color.setAlpha(alpha);

      image.setPixel(x, y, color.rgba());
    }
  }

  pixmap = QPixmap::fromImage(image);
}

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I've read about the now-obsolete QPixmap method called setAlphaChannel(), but it's implementations are platform-dependent.