Pictures on the ST

Pictures on the ST

Post by Andrew Kri » Thu, 21 Jun 1990 23:48:00



I recently saw some IFF pictures on my friend's Amiga and was greatly
impressed.  They made most of the Spectrum pictures I've seen look like water
colors.  Is there a better graphics format than Spectrum for the ST?  Does
the Amiga 2000 have a higher resolution than the 520 ST?  Is this a result of
IFF displaying more colors or something?

I also have some GIF pictures I've been trying to view on my ST.  I haven't
had much luck with PD GIF viewers, so I used a GIF to Spectrum conversion
program instead.  Some of these GIF files were 100-200K, but the Spectrum
pictures produced by the coverter were always around 51K.  Needless to say,
the resolution was horrible!  Is this a fault of the conversion program?

Is there anyway to create/view high resolution color pictures on the ST that
approach GIF and IFF?  I've been very disappointed with what I've seen so
far.
--
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=  Andrew Krieg                         Marvel Historian                =

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Pictures on the ST

Post by Richard L » Fri, 22 Jun 1990 04:28:28


| [...]
|I also have some GIF pictures I've been trying to view on my ST.  I haven't
|had much luck with PD GIF viewers, so I used a GIF to Spectrum conversion
|program instead.  Some of these GIF files were 100-200K, but the Spectrum
|pictures produced by the coverter were always around 51K.  Needless to say,
|the resolution was horrible!  Is this a fault of the conversion program?
| [..]

I've converted a number of GIFs to SPUs with a pd program called bgif.
As you say, the result is always a file of size 51K, and is somewhat
disappointing.  I have other Spectrum pictures which look better despite
being _smaller_ files -- is it that bgif does not take full advantage of
Spectrum's capabilities?  _Are_ there better converters or GIF viewers?

While I'm on the subject -- I have Spectrum pictures with file types
SPC, SPS, and SPU.  My slide programs do not work on one of these types
(SPC?); where can I find a converter or viewer for it?  Thanks for any
info.

 
 
 

Pictures on the ST

Post by Scott Yeli » Fri, 22 Jun 1990 12:02:01


Quote:>I've converted a number of GIFs to SPUs with a pd program called bgif.
>As you say, the result is always a file of size 51K, and is somewhat
>disappointing.  I have other Spectrum pictures which look better despite
>being _smaller_ files -- is it that bgif does not take full advantage of
>Spectrum's capabilities?  _Are_ there better converters or GIF viewers?

Ok, I've got to say something....  I love images-- I have a scanner.
I also have not had any problems converting GIFS and the images usually
look EXACTLY like the conversion file.

Of course, I ONLY CONVERT GIFS OF 320x200 SIZE!

I use pbm and other utilites to accomplish this task.

I also find that most images can be converted to 320x200 with 16 colors
and saved in IFF format.  In this way I can get .p[ci]1 pics also.

With possible future pbm utilities for Atari formats, this process should
become painless.  The conversion takes a while with the ST so I normally
a sun sparcstation (usually with a process reniced to -15 or so...)--
HOWEVER, I have not looked into to it, but it would be nice to get PBM to
compile under TOS AND MINIX ST!
--
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Pictures on the ST

Post by Ali Oz » Wed, 27 Jun 1990 23:33:40



> ...  Spectrum does this, and can switch the palette quickly
>enough to let you choose 48 of the possible 512 colors per each of the 200
>lines in a low-resolution screen.  ...
> ... there are Amiga programs that do similar tricks as Spectrum
>does on the ST, giving you all 4096 colors at once.

Yes, there are. But you can get 4096 colors at once using the Amiga HAM mode
(in 320x400 resolution) without the program doing any tricks or the processor
having to do any extra work. This mode essentially compresses 4096 colors (12
bits) down to 6 bits by encoding a pixel color as either one of 16 absolute
entries (selectable as first 16 entries in the color palette) or as the
previous pixel color plus a replacement of one color component (R, G, B).
Photographs of people and scenery and most ray traced pictures end up looking
great in this mode; some pictures suffer from fringing effects, though.

It's of course true that there are programs that resort to changing the color
palette on the fly to give you modes such as 4096 colors at once in hi-res.

Ali Ozer

 
 
 

Pictures on the ST

Post by Joe Smi » Wed, 27 Jun 1990 12:30:55



>I recently saw some IFF pictures on my friend's Amiga and was greatly
>impressed.  They made most of the Spectrum pictures I've seen look like water
>colors.  Is there a better graphics format than Spectrum for the ST?  Does
>the Amiga 2000 have a higher resolution than the 520 ST?  Is this a result of
>IFF displaying more colors or something?

Atari ST resolutions:
        320x200, 16 colors out of 512, regular color monitor.
        640x200,  4 colors out of 512, regular color monitor.
        640x400,  2 colors, black and white (31Khz) monitor.

Amiga resolutions:
        320x200, 2, 4, 8, 16, or 32 colors out of 4096.
        320x200, 64 colors out of 4096.  (limitation on 2nd set of 32 colors)
        320x200, 4096 out of 4096.  (some limitation on adjacent colors)
        640x200, 2, 4, 8, or 16 colors out of 4096.
Plus an additional set of 11 resolutions with 400 lines (interlaced) instead
of 200 lines.  (The screen may flicker in interlace mode, but it matches the
NTSC standard RS-170, allowing easy interface to genlocks and VCRs.)

Amiga programs switch between any of the 22 resolutions to any other, without
rebooting, all on the same monitor.  (Or have the top half of the screen in
one resolution and the bottom half in another.)

An upgrade to the Amiga provides new resolutions:
        1280x200, 4 colors out of 64 for 35 nanosecond pixels for NTSC (15Khz)
        1280x400, 4 colors out of 64 for 35 nanosecond pixels for NTSC (15Khz)
        640x480, 4 colors out of 64 for VGA (31Khz) compatible monitors
        640x960, 4 colors out of 64, interlaced at 31Khz

Sorry, I don't know for sure the resolutions on the TT.
Does the TT support 640x400 resolution on a color monitor?
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Pictures on the ST

Post by Peter Cher » Thu, 28 Jun 1990 00:54:03




>>I recently saw some IFF pictures on my friend's Amiga and was greatly
>>impressed.  They made most of the Spectrum pictures I've seen look like water
>>colors.  Is there a better graphics format than Spectrum for the ST?  Does
>>the Amiga 2000 have a higher resolution than the 520 ST?  Is this a result of
>>IFF displaying more colors or something?

>Atari ST resolutions:
>    320x200, 16 colors out of 512, regular color monitor.
>    640x200,  4 colors out of 512, regular color monitor.
>    640x400,  2 colors, black and white (31Khz) monitor.

>Amiga resolutions:
>    320x200, 2, 4, 8, 16, or 32 colors out of 4096.
>    320x200, 64 colors out of 4096.  (limitation on 2nd set of 32 colors)
>    320x200, 4096 out of 4096.  (some limitation on adjacent colors)
>    640x200, 2, 4, 8, or 16 colors out of 4096.
>Plus an additional set of 11 resolutions with 400 lines (interlaced) instead
>of 200 lines.  (The screen may flicker in interlace mode, but it matches the
>NTSC standard RS-170, allowing easy interface to genlocks and VCRs.)

>Amiga programs switch between any of the 22 resolutions to any other, without
>rebooting, all on the same monitor.  (Or have the top half of the screen in
>one resolution and the bottom half in another.)

>An upgrade to the Amiga provides new resolutions:
>    1280x200, 4 colors out of 64 for 35 nanosecond pixels for NTSC (15Khz)
>    1280x400, 4 colors out of 64 for 35 nanosecond pixels for NTSC (15Khz)
>    640x480, 4 colors out of 64 for VGA (31Khz) compatible monitors
>    640x960, 4 colors out of 64, interlaced at 31Khz

The Amiga 3000 and any Amiga with the Enhanced Chip Set may also switch
without rebooting between NTSC and PAL compatible modes.  In PAL mode,
the vertical height is 256 (non-interlaced) or 512 (interlaced).  The Amiga
3000 also contains circuitry to de-interlace the 400 or 512 line modes
that are 320 or 640 pixels across, and output VGA compatible signals.
De-interlacing products are also available for the Amiga 2000.
That is, you may run in 640 x 400 VGA (flicker-free) with 16/4096 colors.

The A2024 monitor gives 1008 x 800 (1008 x 1024 in PAL) in 2 or 4 shades
of gray, for any Amiga.   The Viking Moniterm 1 gives the same resolution
for any Amiga with a video slot.

In addition, the Amiga offers support in the OS for overscan.  It is also
possible to do "dynamic hi-res" or "dynamic HAM", which I gather is akin
to the 512-color ST pictures (same kinds of tricks).

The Amiga also has programmable video modes, so things like 24 frames per
second are possible without hardware modifications.

     Peter
--
     Peter Cherna, Software Engineer, Commodore-Amiga, Inc.

My opinions do not necessarily represent the opinions of my employer.
"If you insist on spending $10000 on a 68030 technology, may we humbly
suggest you buy three Amiga 3000's."

 
 
 

Pictures on the ST

Post by SPL.. » Thu, 28 Jun 1990 08:58:30



Cherna) says:

>     Peter Cherna, Software Engineer, Commodore-Amiga, Inc.

>My opinions do not necessarily represent the opinions of my employer.
>"If you insist on spending $10000 on a 68030 technology, may we humbly
>suggest you buy three Amiga 3000's."

Hmmm...  Seems to be a lot of "propagandizing" on the ol' net lately.
Seems like a Commodore engineer would have better things to do than
read c.s.a.st.  ;-)
  Now, don't start on me.  This is not another shot in the Everlasting
Holy War between Atari-types and Commodore-types.  I did my time in the
trenches, but now I have other concerns than "whose floppy is bigger".
The only reason I've brought it up is that all the talk about the merits of
the Amiga 3000 would seem to be better placed somewhere else.  Yes, it's
a neat machine, and dirt cheap besides; but, if a potential TT-er wants to
learn more about the A3000, let him read comp.sys.amiga (or Byte magazine).
  On the other hand, there seems to be little else to do in c.s.a.st besides
random flaming, so maybe a little advertising would put the bandwidth to
better use.  You could even cross-post to misc.foresale.computers.
  Just one guy's opinion...


 
 
 

Pictures on the ST

Post by L.J.Dick » Fri, 29 Jun 1990 10:12:48



> ...
>The only reason I've brought it up is that all the talk about the merits of
>the Amiga 3000 would seem to be better placed somewhere else.
> ...


Very p'litely said, Steve.  :-)
 
 
 

Pictures on the ST

Post by a.. » Fri, 29 Jun 1990 19:43:48




>> ...  Spectrum does this, and can switch the palette quickly
>>enough to let you choose 48 of the possible 512 colors per each of the 200
>>lines in a low-resolution screen.  ...
>> ... there are Amiga programs that do similar tricks as Spectrum
>>does on the ST, giving you all 4096 colors at once.

> Yes, there are. But you can get 4096 colors at once using the Amiga HAM mode
> (in 320x400 resolution) without the program doing any tricks or the processor
> having to do any extra work. This mode essentially compresses 4096 colors (12
> bits) down to 6 bits by encoding a pixel color as either one of 16 absolute
> entries (selectable as first 16 entries in the color palette) or as the
> previous pixel color plus a replacement of one color component (R, G, B).
> Photographs of people and scenery and most ray traced pictures end up looking
> great in this mode; some pictures suffer from fringing effects, though.

> It's of course true that there are programs that resort to changing the color
> palette on the fly to give you modes such as 4096 colors at once in hi-res.

> Ali Ozer

  Yes, Ali, HAM pics CAN suffer fringes, but if the raytracing programs better
selected the palette, there would be VERY few cases of this.  I find myself
going through some of these raytraces with a paint program and finding that
there are like 4 colors in the base palette that remain black.  They COULD have
used those, but NOoooooo, they're STUPID...  BTW, the Amiga, theoretically can
have 384 different colors per scanline (max. res. 384x480).  And the special
thing you were talking about there, was, for these ST people, 768x480 at 16
different colors per scanline.  Not bad, but I *THOUGHT* they could have done
better.  
 
 
 

Pictures on the ST

Post by a.. » Mon, 02 Jul 1990 23:02:35



> I recently saw some IFF pictures on my friend's Amiga and was greatly
> impressed.  They made most of the Spectrum pictures I've seen look like water
> colors.  Is there a better graphics format than Spectrum for the ST?  Does
> the Amiga 2000 have a higher resolution than the 520 ST?  Is this a result of
> IFF displaying more colors or something?

> I also have some GIF pictures I've been trying to view on my ST.  I haven't
> had much luck with PD GIF viewers, so I used a GIF to Spectrum conversion
> program instead.  Some of these GIF files were 100-200K, but the Spectrum
> pictures produced by the coverter were always around 51K.  Needless to say,
> the resolution was horrible!  Is this a fault of the conversion program?

> Is there anyway to create/view high resolution color pictures on the ST that
> approach GIF and IFF?  I've been very disappointed with what I've seen so
> far.
> --
> =========================================================================
> =  Andrew Krieg                            Marvel Historian                =

> =========================================================================
> = Sheriff Truman:  Do you think they spotted us?                   =
> = Agent Cooper:       Gimme a doughnut.                    - Twin Peaks    =
> =========================================================================

  The IFF pictures you saw were in a format also called HAM.  In which the
Amiga (ANY MODEL) can display all 4096 colors in a max. res. of 384x480 without
doing any weird stuff like Spectrum does.  Also, HAM stands for
Hold-And-Modify.  

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Pictures on the ST

Post by Howard C » Tue, 03 Jul 1990 16:16:58


Well, just to add more deadweight to the dying discussion... I've just
finished porting Fractint 12 from MSDOS to the ST, and along the way I
added some "new" video modes as well. I added 4-color grayscale to the
monochrome resolution, and made the medium resolution 16 colors, and
the low resolution has a palette of 256 colors. From my calculations,
the available palette is 512 * 511 / 2 = 130816 distinct colors. The
4 color grayscale is nothing wonderful to look at. Downright ugly, to
be honest, but it would look good on a monitor with high-persistence
phosphor. The low resolution mode looks pretty slick, though. Most of these
fractals look really gorgeous with 256 colors.

The trick is pretty obvious, it seems. Just use two screens, and flip the
physical page on every vertical blank. This effectively doubles the number
of bits per pixel, and as expected, squares the number of colors that can
be displayed at once on screen. It also introduces an incredibly annoying
flicker... But hey, Amigans settle for a megapixel display that updates at
15 hertz, 30 hertz is a lot better. Sending 4 complete screens at 15 hertz
on the ST would give, what ... 64K displayable colors out of, oh... 36 bits
worth of palette. Not that it'd be incredibly worthwhile.... You'd really
need the same kind of monitor that the Amigans use - an intelligent one
that assembles the video frames in an internal buffer.

Going to monochrome is a slightly different story. If you just use two screens
and flip back and forth between them, you'll get dark, half-light, and light.
To get 4 distinct levels of grayscale, or to make the significant bits really
significant, you have to display them onscreen for a longer period of time.
But that's pretty easy too... So, the 70 hertz monochrome video is split up
into a low-significance image sent for one-third of the time, or 23.3 hertz,
and the high-significance image is sent at 47 hertz. The flicker here is
really really noticable. Anything slower than 30 hertz will be, of course.
Turning the brightness down or getting a monitor with high-persistence
phosphor would cure that problem....

Ok, I guess I've rambled long enough. I've had a lot of fun getting this code
working, and I personally think the doubled video modes are kinda neat, even
if the monochrome flicker is as obnoxious as a fluorescent light...

Now... If you're really really crazed, you can do vertical blank image switching
*and* horizontal scan palette switching at the same time. I don't think it's
really practical for general purpose drawing, or for drawing fractals either,
for that matter. Limiting color selections on a per-scanline basis just seems
like too much hassle to deal with. But if you wanted to try it, you could
draw yourself... 256 * 3 swaps per line * 200 lines = 153600 colors per
screen. I guess that's a bit excessive, given only 130K colors in the palette.

SO.... I hope this discussion is really, truly dead now, so we can get to
more interesting things. Meanwhile I'll be submitting fractint for posting
Real Soon Now. (But sometimes, ya gotta wonder. Why are you spending all
these cycles drawing these silly pictures???)
--

  ... the glass is always greener on the side ...

 
 
 

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thanks

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