On Thu, Nov 23, 2017 at 03:14:46PM -0500, Ilia Mirkin wrote: > On Thu, Nov 23, 2017 at 2:09 PM, Ville Syrjälä > <ville.syrjala@xxxxxxxxxxxxxxx> wrote: > > On Thu, Nov 23, 2017 at 01:59:28PM -0500, Ilia Mirkin wrote: > >> We need to shift the values up, otherwise we'd end up with a negative > >> shift. This works for up-to 16-bit components, which is fine for now. > > > > Shouldn't we actually replicate the high bits in the low bits? > > Not entirely sure what you're proposing... > > Ideally we wouldn't be lazy and pass e.g. 16-bit values to MAKE_RGBA > which would then shift down as necessary (and even there, you could > end up with off-by-1's maybe?). For e.g. 0xff, that should become > 0x3ff but with my code will become 0x3fc. Exactly the issue. > But for other values, it's > less clear what to do with the low bits. I figured it didn't really > matter. > > Do you have a concrete proposal? The usual thing would be just (value) * 0x3ff / 0xff or ((value) << 2) | ((value) >> 6) -- Ville Syrjälä Intel OTC _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
