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VGA Clown to various formats

Posted: Tue Jul 08, 2008 6:35 pm
by ROWBEARTOE
This was one of my favorite pictures that showed off 256 color VGA graphics. I was always interested in how other older computers could translate it. This is one of those rare times I have a Apple IIGS example (16 colors per scan line from 4,096). For the fun of it, I included a CGA conversion- perhaps the best 4 color CGA picture I've ever seen. This is also what is becoming more rare for me to witness, the Amiga 4096 color HAM6 pictures looks better than Spectrum 512. Unless of course you focus on the random bright green colors that show up around the eyes and black makeup. Photochrome easily looks the best.

Re: VGA Clown to various formats

Posted: Tue Jul 08, 2008 8:59 pm
by beastie
Nice comparision. This CGA example especially ;-)

It's a pity we cannot see the pictures on the real machines standing side by side, but still we can get the general idea and differences. It's enough for some creative thinking.

:cheers:

Re: VGA Clown to various formats

Posted: Wed Jul 09, 2008 12:12 pm
by teh3pwner
nice pictures, the CGA 4-color looks cool, the photochrome one looks best IMHO, HAM6 looks nice too but its a little blured :lol: :lol: :lol:

Re: VGA Clown to various formats

Posted: Thu Jul 10, 2008 6:15 am
by ROWBEARTOE
Interesting 16 color conversions. First I used the Spectrum 512 to 16 color Degas program that came with Spectrum 512. The other program I used was BGIF which allows me to convert GIF (in this case the original 256 color picture) to a dithered 16 colors. These are my results.

Re: VGA Clown to various formats

Posted: Thu Jul 10, 2008 6:27 am
by simonsunnyboy
Did you try Speed Of Light on the 256col gif?

BTW Bgif is poor at converting GIF to PI1 but pretty nice when doing SPU...at least for my tries so far.

Re: VGA Clown to various formats

Posted: Thu Jul 10, 2008 6:47 am
by ROWBEARTOE
This is the GIF picture incase you want to try converting it to various formats. To bad we cant get a hold of the photograph. Converting high resolution 24-bit pictures just looks a lot better.

Re: VGA Clown to various formats

Posted: Thu Jul 10, 2008 12:24 pm
by bullis1
ROWBEARTOE wrote:This is the GIF picture incase you want to try converting it to various formats. To bad we cant get a hold of the photograph. Converting high resolution 24-bit pictures just looks a lot better.


I think I have a high-colour JPG of that clown somewhere, on a CD from Corel Corp. I'll take a look later.

Re: VGA Clown to various formats

Posted: Thu Jul 10, 2008 8:23 pm
by Desty
Man, the Photochrome pictures are amazing. I had one of an alien on a disk year back, but it seemed a bit flickery.

Re: VGA Clown to various formats

Posted: Thu Jul 10, 2008 11:32 pm
by ROWBEARTOE
Desty wrote:Man, the Photochrome pictures are amazing. I had one of an alien on a disk year back, but it seemed a bit flickery.


I don't post or keep pictures that have to much flicker. I use the "non-flicker" method for the 512 color ST. But if it flickers to much, then I don't keep it. Every photochrome I've posted looks great on the real ST with little to no flicker. =)

Re: VGA Clown to various formats

Posted: Fri Jul 11, 2008 10:41 am
by Desty
Even the Spec 512 job on the clown is great, and more accurate-looking than the Amiga HAM6 version, which seems to introduce some colour artefacts on some edges (e.g. nose bridge, eyelashes). Photochrome pics would make a nice little title screen/static intro, if you had enough CPU to fade in/out and play a chiptune in the background, and diskspace to store the thing :)

Come to think of it, how long to they take to load and display? ISTR a while with the demo images on my old Photochrome disk?

Re: VGA Clown to various formats

Posted: Wed Jul 30, 2008 9:30 pm
by MiggyMog
The pixel twins managed to do this. I was going to upload a disk image of it but I think my Satandisk SD card just corrupted :roll:

Re: VGA Clown to various formats

Posted: Fri Jul 20, 2012 6:59 pm
by dml
Photochrome used a bunch of tricks combined - each having a small impact - to try to match the original colour at that pixel. Some of it is obvious but some a bit less so.

* Reload the entire palette as many times as possible, per scanline. This gets you pretty far but is just an optimised version of what Spectrum512 always did.
* Render 2 images and strobe them. On interlaced displays you get some benefit from the fact that scanlines are blurred both positionally (vertical blurring) and temporally (persistence) so scanlines aren't really completely separate between half-frames. There's some inherent flicker but the blurring effects help average colours from multiple images.
* Allocate pixels using error distribution, and distribute the error across the 2 images (as well as outwards in 2D as usual) so the strobing will turn 'colour error' into 'flicker error' which gets absorbed by the TV to an extent.
* Allocate new palette values as part of the error distribution as much as possible, so the 'wrong' colour used in one field is compensated by an opposite colour on the next field.
* Use a different error size for different machine specs. Colour error on STE is half that of an ST.

The rest is down to using a good dithering/error distribution method and rock solid palette loader.

There was a fullscreen version of this stuff, but it couldn't manage so many colours. I can't really remember why - maybe just older code. I think it was used in the 'Tobias Richter' slideshow disc... (??)

There was another issue with PCS - some machines (like my Mega4) had a strange problem where the shifter loaded the palette a cycle 'late' and it produced noisy 1-pixel vertical lines sometimes, depending on luck when you booted the machine. This couldn't be compensated by the CPU in the usual way (for Timer-B rasters) so PCS delayed using newly loaded palette indexes for 1 pixel to hide the artifact.

I remember trying an STE blitter version of the palette reloader but i don't remember the outcome now. Probably caused some issue or other or I would have used it.

(I suspect the error diffusion stuff in PCS could have been improved further given a bit more effort - I'm scared to look :-)

Re: VGA Clown to various formats

Posted: Wed Aug 15, 2012 8:54 pm
by MiggyMog
(I suspect the error diffusion stuff in PCS could have been improved further given a bit more effort - I'm scared to look


I look forwar to an newly optimised version with a batch mode ;-)

Re: VGA Clown to various formats

Posted: Thu Aug 16, 2012 4:21 am
by DarkLord
MiggyMog wrote:
(I suspect the error diffusion stuff in PCS could have been improved further given a bit more effort - I'm scared to look


I look forwar to an newly optimised version with a batch mode ;-)


It really is nice to see Doug active here! :)

Re: VGA Clown to various formats

Posted: Thu Aug 23, 2012 11:30 am
by dml
MiggyMog wrote:I look forwar to an newly optimised version with a batch mode ;-)


A new version with batch- & cross-conversion is on the cards. Which is a probably bit strange after the enormous delay but there are still a few things I wanted to fix/improve out and that was one of them.

Re: VGA Clown to various formats

Posted: Thu Aug 23, 2012 11:42 am
by Shredder11
Photochrome 4 was one of the main reasons I stayed with the Atari STE until summer 2000; prior to using Photochrome I had been looking and trying hard to get a PC to get online with. In the mid to late 1990s I had seen what could be done with a modern PC and was seduced, but not entirely as I began to realise just how powerful my STE was in comparison. So I am always very interested in anything to do with the mighty Photochrome! :cheers:

Re: VGA Clown to various formats

Posted: Thu Aug 23, 2012 11:47 am
by CiH
A new version with batch- & cross-conversion is on the cards. Which is a probably bit strange after the enormous delay but there are still a few things I wanted to fix/improve out and that was one of them.


Wahey! Thanks Doug! :cheers:

Re: VGA Clown to various formats

Posted: Mon Aug 27, 2012 6:45 pm
by dml
An early version of PCS 5 is on my site now. Updates will follow.

http://www.leonik.net/dml/sec_pcs.py

Re: VGA Clown to various formats

Posted: Sat Mar 30, 2013 6:14 pm
by waSTE
Seeing that clown brings back lots of memories! Back when simply opening a file like that was quite magic

Re: VGA Clown to various formats

Posted: Fri Aug 02, 2013 11:49 am
by FlaminJoe
As soon as I saw the title I knew exactly what it was. I can't remember how long it's been since I've seen it and the name of the paint program I used at the time escapes me. Memories....