Apple IIgs video modes?
ca...@busop.cit.wayne.edu
I am new to Apple IIgs computers and I was wondering if someone could list
its video mode specs, like resolution and color. From what I remember I
heard it could do a maximum of 256 colors on screen, but only 16 different
ones per scanline out of a palette of 4,096. But then I've seen these
pictures that claim to be 3,200 colors. So what's the scope?
Thanks
-
Carl Mueller
Wayne State University
email: ca...@busop.cit.wayne.edu
hochs...@urz.unibas.ch
The facts in your post are all correct but I'll try to put it systematically:
RESOLUTION (GS specific)
320x200, every pixel 4 bits deep, so 16 principally 16 colors possible
640x200, every pixel 2 bits deep, so 4 colors here in principal
But you aren't restricted to the same choice of colors all over the entire
screen. Instead, the GS uses CLUTs (color look-up tables) called palettes,
to determine the hue to display.
Standard display modes defined by Apple can use the following number of
palettes (one scan line can only have one palette at a time):
- 320x200 ('320 mode') 16 palettes per screen so 16*16=256 different
hues per screen
- 640x200 ('640 mode') 16 palettes also. But since each pixel only
uses 2 bits, you have space for more 'positions' inside the palette:
4 'mini-palettes'. The first stands for the 1st, 5th, 9th pixel column,
the second for the 2nd, 6th, 10th pixel column and so on. By using
dithering (two adjacent colors blend into a new color) and clever
minipalettes you can get 16 different colors per palette. Since you
have 16 palettes as in 320 mode, you can also get 256 different hues here.
(Unfortunately many paint programs only support a screen to have one
palette, so the the entire screen is restricted to 16 different hues.)
Now we come to the number of colors we can choose from: The GS hardware
supports 16 different levels of each basic video color red, green and
blue (RGB). Makes 16*16*16=4096 different hues.
So much for the standards: 256 colors out of 4096 per screen.
The trick for the 3200-color screen modes is, that the program displaying
those pictures changes palettes on the fly, i.e. while the electron beam
moves from one scan line to the next. Since you have 200 scan lines with
16 hues each you get 16x200=3200 which stands for very realistic pictures
if the palettes are chosen carefully. The disadvantage is, that a un-
accelerated GSes are kept busy almost only to switch palettes.
Huh, that was a long one. I hope it was clear enough...
-- Urs
| BRIGHT SOFTWARE | * A P P L E I I F O R E V E R * |
| Urs Hochstrasser | Actually in Development: C H E M I X |
| Strassburgerallee 79 | Pseudo: CodeBurger (binary sauce) |
| 4055 BASEL, SWITZERLAND | InterNET: HOCHS...@URZ.UNIBAS.CH |
ca...@busop.cit.wayne.edu
>The trick for the 3200-color screen modes is, that the program displaying
>those pictures changes palettes on the fly, i.e. while the electron beam
>moves from one scan line to the next. Since you have 200 scan lines with
>16 hues each you get 16x200=3200 which stands for very realistic pictures
>if the palettes are chosen carefully. The disadvantage is, that a un-
>accelerated GSes are kept busy almost only to switch palettes.
>
>Huh, that was a long one. I hope it was clear enough...
-
ca...@busop.cit.wayne.edu
>Huh, that was a long one. I hope it was clear enough...
>
>-- Urs
>
>| BRIGHT SOFTWARE | * A P P L E I I F O R E V E R * |
>| Urs Hochstrasser | Actually in Development: C H E M I X |
>| Strassburgerallee 79 | Pseudo: CodeBurger (binary sauce) |
>| 4055 BASEL, SWITZERLAND | InterNET: HOCHS...@URZ.UNIBAS.CH |
It was very clear, that's pretty much how I guessed it worked. (Sorry about
that last post).
Thank you!
Ian Schmidt
>
>I am new to Apple IIgs computers and I was wondering if someone could list
>its video mode specs, like resolution and color. From what I remember I
>heard it could do a maximum of 256 colors on screen, but only 16 different
>ones per scanline out of a palette of 4,096. But then I've seen these
>pictures that claim to be 3,200 colors. So what's the scope?
Easy. 3200 color displayers swap the palettes while the screen is refreshing.
It's basically a software version of the Amiga HAM technique.
--
Ian Schmidt - Two Meg Software: irsman@{iastate.edu | aol.com}
"I will choose a path that's | Author of AudioZap, MODZap, and more.
clear: I will choose free will" | Co-author of SoundConvert and DeskTracker.
- N. Peart, 1980 | Coder and Musician for the GS<>IRC.
Lim Thye Chean
:
: I am new to Apple IIgs computers and I was wondering if someone could list
: heard it could do a maximum of 256 colors on screen, but only 16 different
: ones per scanline out of a palette of 4,096. But then I've seen these
: pictures that claim to be 3,200 colors. So what's the scope?
OK, a simple summary. There are 2 video modes: 320 x 200 and 640 x 200.
There are 4096 colours to choose from. On 320 x 200 mode, a palette can
contain 16 colours. On 640 x 200 mode, a palette can contain 4 colours or
15 dithered colours. Each line has a palette.
On either mode, you can have up to 16 palettes per screen. That is, if you use
16 palettes on 320 x 200 mode, and since each palette contains 16 colours, you
get up to 16 x 16 = 256 colours. Under 640 x 200 mode, that is 4 x 16 = 48
colours.
If there is a program on the background swapping palettes, you can have up
to 200 palettes displayed at one time. That is, each line has its own palettes.
So you can have 16 x 200 = 3200 colours. But I have never seen a 3200 picture
uses more than 256 colours.
: Thanks
You are welcome.
: -
: Carl Mueller
: Wayne State University
: email: ca...@busop.cit.wayne.edu
--
%% GS Lover Loves GS %% Author of Super Magic 3 & Mandelbrot II GS
%% and Avatar too. %%
Lim Thye Chean: Lim is my surname. My name is Thye Chean.
My address: LTC...@ISS.NUS.SG, or 9, College Green, Singapore 1129
Yong Su Kim
>If there is a program on the background swapping palettes, you can have up
>to 200 palettes displayed at one time. That is, each line has its own palettes.
>So you can have 16 x 200 = 3200 colours. But I have never seen a 3200 picture
>uses more than 256 colours.
Actually, that is because a lot of the 3200 colour pictures that are
floating around have been converted from GIFs. In the GIF format,
pictures are limited in that they can only display 256 colours on the
screen at one time, although they have a much larger range of colours
which can be chosen to be one of the 256 colours. I'm pretty sure
that is the case, but if I am wrong, someone can correct me.
It would not be too difficult to generate a 3200 colour picture using
a 3200 colour paint program like DreamGrafix. Given some of the
advanced graphics tools for dealing with multiple palettes in
DreamGrafix, it would be rather trivial to draw something with 3200
colours. Of course, making a good looking picture with 3200 colour is
another matter since the tools do not necessarily make the artist...
Actually, come to think of it, I do remember seeing some 3200 colour
pictures done by an artist called Ferrari floating around which used
more than 256 colours. You could run the picture through SuperConvert
and it would tell you how many colours were used, but I don't have the
picture anymore so I can't give you a precise number.
I know that DreamGrafix is still selling since I've seen their ads in
A+/Incider, and it's a shame that there hasn't been a big effort by
people to exploit the 3200 and 256 colour mode on the Apple IIGS.
DreamWorld is the only company that I can thinkin of which has a real
viable commerical product which truly utilises the special graphics
modes on the GS.
Of course, there was Prizm and that other 3200 colour paint program
whose name escapes me which was hyped up but never released for some
mysterious reason.
At least DreamGrafix is still around and shipping...
--
===============================================================================
Yong Su Kim, Class of 1993 | Internet: y...@cunixb.cc.columbia.edu
Columbia College, Columbia University | or yk...@cs.columbia.edu
Paul Schultz
>
>Of course, there was Prizm and that other 3200 colour paint program
>whose name escapes me which was hyped up but never released for some
>mysterious reason.
>
>At least DreamGrafix is still around and shipping...
>
latest incider/A+ issue..... for what its worth!
Paul Schultz
--
===============================
Internet: sch...@pd-dom.wl.com
===============================
Richard J Wifall
> FYI, for what its worth, Prizm was advertised in the LRO ad in the
> latest incider/A+ issue..... for what its worth!
PriZm or priSm ?? Prizm is a buggy desktop debugging program for
the orca programming environment by ByteWorks. Prism is a vaporware
graphics conversion program by Ron Mercer.
> Paul Schultz
--
-- Richard Wifall - rwi...@nmsu.edu - 65816 programmer for hire
Paul Schultz
>In article <1993Apr24....@wl.com> sch...@wl.com (Paul Schultz) writes:
>
>> FYI, for what its worth, Prizm was advertised in the LRO ad in the
>> latest incider/A+ issue..... for what its worth!
>
> PriZm or priSm ?? Prizm is a buggy desktop debugging program for
>the orca programming environment by ByteWorks. Prism is a vaporware
>graphics conversion program by Ron Mercer.
>
the ad myself!
LRO had this text under the ad:
New Concepts
PRISM
MultiConverter for your GS. Convert any Apple IIgs, IBM, Macintosh and
Next graphic files to 16, 256 and 3200 color files on your Apple IIgs.
$38.00
Jay Krell
impossible to draw with, since the colors are divided into minipalettes
for a quarter of the pixels each.
:wq
--
--Jay, jay....@cornell.edu
Steven T Chiang
>640 mode can actually display 256 or 3200 pure colors; it's just
>impossible to draw with, since the colors are divided into minipalettes
>for a quarter of the pixels each.
640 mode has 4 pure colors per line, 64 per screen with
multiple palette and 800 using the equivalent of 3200 color mode in
640 mode. That's pure colors though.
To get 16 colors per line the colors are dithered, not pure.
It is possible to draw in that mode. Check out the awesome work by Bo
Monroe and Donald McIntosh... (some is in HyperStudio and other stuff
is in Studio City)
> --Jay, jay....@cornell.edu
Steven Chiang Order - DreamGrafix: The ONLY 16/256/3200
st...@cunixb.cc.columbia.edu color paint program for the Apple IIGS.
America On_Line: DWS Steve
Genie: S.Chiang4 Apple IIGS Forever!
Jay Krell
>multiple palette and 800 using the equivalent of 3200 color mode in
>640 mode. That's pure colors though.
give each line's palette 16 different colors. Each pixel has a choice of 4 of
these, but all 16 could appear on the line.
You could also mix 640 and 320 modes, using the practical 4 colors per line for
640 mode, giving 4m + 16n colors, where there are m 640 lines and n 320 lines.
:)
In case people don't know the IIGS video (and for the person that asked in
email):
Each line is individually selectable between 640 and 320 modes. Each
line selects one of 16 16-color palettes (or its own 16 color palette if
swapping palettes for 3200 colors). In 640 mode, "The 16 colors in the palette
are divided into four groups of 4 colors each. The first pixel in each
horizontal line can select one of 4 colors from the third group of 4 in the
palette. The second pixel selects from the fourth group of 4 colors in the
palette. The third pixel selects from the first group of 4 colors, and the
fourth pixel selects from the second group, as shown in Table 4-21. The process
repeats for each successive group of 4 pixels in a horizontal line. Thus, even
though a given pixel can be one of 4 colors, different pixels in a line can
take on any of the 16 colors in a palette." (IIGS Hardware Ref, 2nd ed, p. 96)
--
--Jay, jay....@cornell.edu
Michael Kent
>Sorry about that, The ad was in fact for PriSm. I was surprised to see
>the ad myself!
>
>LRO had this text under the ad:
>
>New Concepts
>PRISM
>MultiConverter for your GS. Convert any Apple IIgs, IBM, Macintosh and
>Next graphic files to 16, 256 and 3200 color files on your Apple IIgs.
>
>$38.00
>
>
>Paul Schultz
>
Has anyone tried Prism? How does it compare with SuperConvert or The
Graphics Exchange?
Mike
Scott Gentry
>In article <C5x9r...@cs.columbia.edu> yk...@cs.columbia.edu (Yong Su Kim) writes:
>>
>>Of course, there was Prizm and that other 3200 colour paint program
>>whose name escapes me which was hyped up but never released for some
>>mysterious reason.
>>
>>At least DreamGrafix is still around and shipping...
>>
>FYI, for what its worth, Prizm was advertised in the LRO ad in the
>latest incider/A+ issue..... for what its worth!
Just because LRO advertises something doesn't mean they have the rights or
the product. I know that first hand.
--
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* Intergraph Corporation| AOL: AFL Scott or afls...@aol.com | Dynasty! *
***************** Dallas Cowboys. Super Bowl Champions. ******************
Steven T Chiang
>>multiple palette and 800 using the equivalent of 3200 color mode in
>>640 mode. That's pure colors though.
>
>I beg to differ Steve. It is completely impractical for drawing, but you could
>give each line's palette 16 different colors. Each pixel has a choice of 4 of
>these, but all 16 could appear on the line.
Well, this was in response to your first post. You had stated
that 640 mode had 16 *pure* colors, which is not the case. 640 mode
has 16 dithered colors or 4 pure colors. If you are using DPaint II
in 640 mode, you only have 4 pure colors to work with. Other paint
programs support 640 w/ the 16 dithered colors. You could have a 640
w/ 3200 dithered colors, but there isn't a real advantage, except your
fonts would look nicer on the screen.
I would agree with you that mixing colors is tough in dithered
color mode... But it is possible, because Bo Monroe does a fantastic
job with 640 mode graphics w/ dithered colors.
>repeats for each successive group of 4 pixels in a horizontal line. Thus, even
>though a given pixel can be one of 4 colors, different pixels in a line can
>take on any of the 16 colors in a palette." (IIGS Hardware Ref, 2nd ed, p. 96)
Right, but the colors are dithered.