Re: 16bpp and above on Linux/XFree86 on 701C

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From: John H. Kim (jokim_at_mit.edu)
Date: Thu Jul 11 1996 - 11:50:01 EDT


On Thu, 11 Jul 1996, Gabor J.Toth wrote:

> > Since then, Bjoern reports he's gotten the latest XFree86 alpha driver
> > to work in 16-bit and 24-bit modes. The 16-bit is displaced by about
> > 40 pixels on the LCD, and the 24-bit mode flickers, but they work for
> > him.
>
> Is it still a palette of 256 colors only? Or is there any way to get
> more then 256 colors on your screen?

The hi-color modes have no palette, palette being defined as a set of
colors from which a smaller number may be displayed simultaneously.
(S)VGA cards use a lookup table to assign a certain color from the
262,144 color (18 bit) VGA palette to each of 256 color slots.

16-bit mode can display 65,536 colors simultaneously.
24-bit mode could display 16,777,216 colors simultaneously if you had
  that many pixels on your screen.

Both of these modes will do >256 colors with ease.
  
The 16-bit mode will actually be *poorer* than 8-bit (256 color) mode
if you're using 256 or fewer shades of the same color. 16-bit mode
assigns 5 bits to RB and 6 bits to G. 8-bit uses a palette based on 8
bits for all RGB. If you're only using 256 shades, the 8-bit mode can
do finer gradiation.

--
John H. Kim       "I stop for red traffic lights" -- bumper sticker 
jokim_at_mit.edu     commissioned by the City of Boston as part of a
MIT Sea Grant     campaign to shed its reputation for bad drivers.


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