From: Andrew Apted <ajapted@netspace.net.au>
  To  : ggi-develop@eskimo.com
  Date: Wed, 24 Feb 1999 11:30:25 +1100

Re: KGI system needs a lot of work

James Simmons writes:

>  I haven't heard from fabrice in a while. I think the patch in now in my
>  hands. I'm still working on some code optimizations and trying to figure
>  out how iplans work for amigas. Anyone knows?

What sort if iplan ?

There is "interleaved bitplanes", where there are N one-bit bitmaps, and
the pixel value comes from the bits at the same (x,y) location from each
bitplane.  The bitplanes are contiguous in memory, so for 4 bit mode
there are 4 bitplanes following each other.

There is "interleaved lines" (ILBM) which is like the above, but each
_line_ is a one-bit bitmap, for example for 5 bit mode you have 5
bitlines for line 0, followed by 5 bitlines for line 1, and so on...

And then there is the ATARI style, where each 16 bits are interleaved,
for example for 4 bit mode you have 4 lots of 16 bits (each 16 bit is a
little `bitline') for the first 16 pixels, then another 4 lots for the
next 16 pixels, and so on...

At least this is my understanding, after looking at the afb and
iplan[2,4,8] code in linux/drivers/video, and the code to the oFbis
library.

Cheers,
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  Andrew Apted   <andrew@ggi-project.org>       \/