🚀 go-pugleaf

In article <10670@chaph.usc.edu> bli@aludra.usc.edu writes:
>I was wondering if anyone here knows how Newtek displays those pseudo-24bit
>images on the stock amiga, and in hires?

As far as I know they use a different color palette on each line. They are
still limited to 16 colors in one line. So you can use Dyna-HIRES only for
pictures with limited color information.

Now I'm coming to the point of this posting. I think the way NewTek does
their Dyna-HAM and Dyna-HIRES is not a good idea.

   1. The Dyna-Modes are not compatible with multitasking:
      Both Dyna-Modes use a lot of processor time to swap the colors
      on each line. It is theoretically possible to write a Dyna-Show
      programm that allows multitasking while vertical blanking, but
      even this would slow things extremly down.

   2. The Dyna-Show programm is not compatible with future Amigas.
      The first version didn't run on '020 and '030. The current
      version is not compatible with the Amiga 3000 because they
      depend on the Chip Memory timing of the 16 bit Amigas.

I think a solution to this could be that all Amiga users try to convince
NewTek and other companies to support not the Dyna-HAM but the SHAM-
standard. As far as I know the SHAM-standard does not come from a 
comercial product.
The idea to increase the sharpness of HAM pictures using different color
registers on each line is great, but the implementation of SHAM has some
advantages over Dyna-HAM. Because it is not possible to change all 16
color registers with the Copper, NewTek had to use the processor to
support the Copper. The SHAM standard solves this by only changing all
foreground colors. These 15 registers can be managed by the Copper alone
and you have no problems with multitasking and if you make the Copper
list with the Operating system, it will be compatible with future Amigas
and Operating Systems. ShowIFF by Chris Weber shows that this is possible
and that it is the way to go. You notice a big speed increase when you 
try to drag a SHAM screen with a user copper list when you run ShowIFF
on the Amiga 3000 under 2.0.
The win of one color when using Dyna-HAM instead of SHAM is really not
worth to give up multitasking. SHAM is really great (I have converted
several GIF pictures which look great) and fully multitasking compatible.
I could be even possible to write a Paint Program for SHAM pictures,
because the program itself can run in fast memory and doesn't loose any
CPU cycles. Of course the screen handling would be slower compared to 
a HAM Paint program because of the user copper list.

>I for one am intersted in displaying 8-bit graphics (max 256 colors) on the
>Amiga, at 640x400. Can anyone suggest a way to do that? What does Newtek do
>to hog the whole amiga while displaying the pic? I suppose it must do quite
>a lot of dithering (anyone knows what kind?) and I heard that it also does
>Gamma correction. Is that all?

The concept of SHAM could probably also be used for hires. This would give
us a SHIRES standard with the same advantages of SHAM. Chris Weber has once
tried to create SHIRES but it doesn't work yet.
I would really like to see that SHAM and may be SHIRES would become standards
on the Amiga for displaying 12-Bit Graphics. We must have a standard here
like the normal Amiga display modes. This would convince other companies
to support such special modes, too.

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