wined3d: universal surface convertor function for unsigned integer color formats(5th attempt)
wine at mkarcher.dialup.fu-berlin.de
Wed Jul 30 06:15:45 CDT 2008
Am Mittwoch, den 30.07.2008, 15:03 +0400 schrieb Victor:
> > You also have to expand types properly, i.e. converting a
> > component from 4-bit to 8-bit isn't just a shift.
> In all places where I saw pixel format conversion before, it was _always_ done
> by shifting components (even in MS-DOS vesa-based applications).
> Your assumption that "converting isn't just a shift" requires link to official
> documentation (i.e. proof), where it is clearly stated that during Blt()
> (from which convert_unsigned_pixels is being called) between different
> surface format, ddraw/d3d converts pixel format by means other than simply
> shifting components. I doubt that in real software ddraw implementation blt
> from 565 to 888 is done by completely recalculating components using floating
> point operations.
Floating point is overkill. The correct way for a 5 to 8 conversion is
"divide by 31, multiply by 255". If you use
bits8 = bits5 << 3 | bits5 >> 2;
you get "bits8 = bits5 * 8.25", which is always less than one off the
correct result. What you do is to repeat the bit pattern infinitely
instead of filling with zeroes on the right hand.
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