RE: [gtk-list] Re: how to convert windows RGB color to GdkColor

["Timothy M. Shead" <tshead sheaddataproc com>]

>    This is not enough.  You then need to add the original value.  I.e.
>
> 	   new_value = (old_value << 8) + old_value;
>
>    Assuming old_value is in [0, 255].
>
> I thought I understood gdkcolors until now.  I have always been under
> the impression that a gdkcolor simply uses a 16-bit value for each of
> red, green, and blue, and that it was converted for whatever hardware
> you were to run on by dividing (so, to run on something with 8-bit
> DACs, you'd right-shift by (16-8) == 8).

Right-shifting to convert from 16bpp to 8bpp works fine:

	0xFFFF (full-bright) becomes 0xFF (full-bright).

But left-shifting doesn't:

	0xFF (full-bright) becomes 0xFF00 (less-than-full-bright).

Adding in the old value is a fast way to scale the values properly, so 0xFF
becomes 0xFFFF.  You can multiply by 257.0 if you prefer :)

Go Lobos!

Tim