| Re: [AD] 6bit limitation of paletted modes. |
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On Sunday 10 April 2005 23:34, StApostol wrote:
> In the frequently asked questions it is stated that ' The VGA hardware
> only uses 6 bits for each color component, which means the red, green,
> and blue values in the palette structure range from 0 to 63'. This can
> be quite a limitation on some cases, and - correct me if I am wrong -
> one that does not apply to modern era hardware.
Correct, although the 6 bit paletted modes still exist.
> Will support for 8bit wide DAC be available in the post-4.2 versions?
It is one of the things that is on the list, yes.
> (This is probably interconnected with the drop of DOS support for
> future versions).
It could be done without doing that - Allegro could support 6 and 8 bit
palettes (see below).
> More to the point, how extensive internal changes
> will be needed for this?
A lot. There's a great deal of code in Allegro, not to mention user code,
that assumes RGB components in a palette range from 0-63.
How to handle that is not clear to me yet, but it could be dealt with in
the compatibility layer if a PALETTE is always 0-63 and the new AL_PALETTE
is something a bit different where RGB values may have different ranges
(0-63, 0-255, 0.0-1.0 all making sense here).
Best to check what Bob wrote on the subject (if anything) in his gfx API
draft.
Evert