From: Geert Uytterhoeven <Geert.Uytterhoeven@cs.kuleuven.ac.be>
  To  : ggi-develop@eskimo.com
  Date: Mon, 14 Sep 1998 13:43:24 +0200 (CEST)

Re: GT_2BIT?

On Sat, 12 Sep 1998, Andrew Apted wrote:
> Stefan writes:
> >  On Sat, 12 Sep 1998, Andrew Apted wrote:
> >  
> >  > Q: do we upgrade the drivers for the new scheme, or what ?
> >  
> >  I have missed something here... what new scheme?
> 
> Graphtypes now have four fields: the `scheme' field (which can be
> GT_TEXT, GT_PALETTE, GT_TRUECOLOR or GT_GREYSCALE), the `subscheme'
> field (a few special uses, like specifying reverse bit/byte order), and
> the `depth' and `size' fields (depth specifies number of bits of usuable
> color info, and size is the pixel width in bits.  EG: 15/16 and 24/32).
> 
> The old GT_xxBIT defines are mainly for compatibility, and are defined
> as follows:
> 
>     #define GT_TEXT16       GT_CONSTRUCT(4, GT_TEXT, 16)
>     #define GT_TEXT32       GT_CONSTRUCT(8, GT_TEXT, 32)
>     #define GT_1BIT         GT_CONSTRUCT(1, GT_PALETTE, 1)
>     #define GT_2BIT         GT_CONSTRUCT(2, GT_PALETTE, 2)
>     #define GT_4BIT         GT_CONSTRUCT(4, GT_PALETTE, 4)
>     #define GT_8BIT         GT_CONSTRUCT(8, GT_PALETTE, 8)
>     #define GT_15BIT        GT_CONSTRUCT(15, GT_TRUECOLOR, 16)
>     #define GT_16BIT        GT_CONSTRUCT(16, GT_TRUECOLOR, 16)
>     #define GT_24BIT        GT_CONSTRUCT(24, GT_TRUECOLOR, 24)
>     #define GT_32BIT        GT_CONSTRUCT(24, GT_TRUECOLOR, 32)
> 
> LibGGI makes use of this new info (which is in ggi/types.h), but the KGI
> drivers are still using the old enumerated graphtypes in kgi/types.h.

Amiga can do 1-8 bitplanes. Atari does 1/2/4/8/16 interleaved bitplanes, NeXT
has 2 bpp greyscale.

Even if you know that you have an 8 bpp screen, how do you know that it's
packed, bitplanes, interleaved bitplanes? And then I'm not talking about
endianness (e.g. packed 4 bpp is 2 pixels in 1 byte: AB or BA?).

Sorry if my comment is silly, I don't look at all the KGI internals.

Greetings,

						Geert

--
Geert Uytterhoeven                     Geert.Uytterhoeven@cs.kuleuven.ac.be
Wavelets, Linux/{m68k~Amiga,PPC~CHRP}  http://www.cs.kuleuven.ac.be/~geert/
Department of Computer Science -- Katholieke Universiteit Leuven -- Belgium