Painting data always as 16-bit color

Hello!

I'm developing an interface application for embedded Linux where the screen system is a 16-bit color system (5-6-5). In order to prevent unnecessary processing consumption, I need to guarantee that the Qt interface only draws on the screen using 5-6-5 color system (if it tries to do otherwise, the system will have to convert it to its 5-6-5 definition, consuming processing to do this).

How do I configure this?

I did manage to find how to guarantee that QPixmaps will be shown in 16-bit colors:
Code:

QPixmap::fromImage(QPixmap(file_name).toImage().convertToFormat(QImage::Format_RGB16))
but that don't include the general drawings, such as when a QWidget is shown or when some QwtPlotCurve s are drawn in a QwtPlot.

So how can I configure this at a "global scope"?

Thanks,

Momergil