Odd - Interesting - Forgotten

[Mark Swift]

Hi,

I was browsing through my old QL disks looking for inspiration recently.
Instead I found a couple of programs that were interesting but would normally never see the light of day again.

There's actually no real reason to post them here.
...however, I must have spent quite some time writing them so it would be a shame not to give them a bit of air time.

BIGCHARS.zip

(3.38 KiB) Downloaded 50 times

09 Aug 1988 - I seem to remember writing this so that I could add titles to some VHS videos.

ATAN1.zip

(789 Bytes) Downloaded 45 times

03 Sep 1988 - This works out equivalents to ATAN(1) i.e. 2*ATAN(2/5)+ATAN(1/41)
I have no idea why I wanted this, or how I even worked out how to do it

HALFTONE.zip

(1.79 KiB) Downloaded 47 times

11 Jan 1990 - I think I wanted to see if I could display images better by making use of halftones.
I tested with a generated function but didn't get to the point of testing it with a real photo.

Anyway... I wondered... has anyone else written something similar?
i.e. odd, interesting but with no particular theme except time and effort.

[bwinkel67]

11 Jan 1990 - I think I wanted to see if I could display images better by making use of halftones.
I tested with a generated function but didn't get to the point of testing it with a real photo.

HALFTONE.jpg

This one is interesting....In trying to understand this, I asked Google what the difference between dithering and halftoning is, which in turn now asks its AI:

While both halftoning and dithering are techniques used to simulate continuous tones with limited color options, the key difference is that halftoning typically uses a structured pattern of dots of varying sizes to create shades, while dithering achieves a similar effect by randomly placing dots of the same size, often with a pre-defined pattern to control the distribution; essentially, halftoning focuses on dot size variation within a structured grid, while dithering relies on the random placement of dots to create the illusion of gradation.

So primarily, the difference is structured vs random patterns? Is that then something that could be added to Photon to add additional options for converting JPEGs besides 25/50/75% dithering?

[dilwyn]

Thank you Mark. Nice programs.

I could have done with bigchars back in the late 80s if I'd known about it. I lived near two brothers who were starting a small night club and cafe bar called Satz in Bangor. Their parents owned the newsagent where I bought my computer magazines on the corner of my street at the time, and they'd cottoned on to me writing programs and working in broadcasting from talking to me when I bought computer mags from them, and asked if I could make them a video to run continuously on screens in the cafe bar and nightclub.

So I painstakingly wrote routines to draw big text which got overlaid on colourful backgrounds LBYTESed to the screen. At one stage I did an all-night programming session to try to meet their deadline and got into trouble for oversleeping and turning up an hour late to work . Rather than run it on a QL (they were afraid of it getting stolen or MDV cartridges failing) they just recorded it as continuous VHS tapes, the longest duration ones they could find, possibly running it on half speed record/playback to double its length IIRC, and asking me to record new text displays from time to time. I didn't get paid directly for it - it was so bad I wouldn't have accepted payment - but they did occasionally let me into Satz free of charge.

The BASIC program drawing the text was embarrassingly slow and nowhere near as good as yours, but they seemed to like the fact it was colourful and slowly and methodically drawn it did seem to catch people's attention. Looking back, my efforts were hilariously bad, but at least I derived a lot of satisfaction seeing it running there inside through the window for a year or so whenever I passed until they could afford something better! That program eventually became my Vision Mixer years later, without the big text drawing routines - I'd lost or deleted the original routines by then, like a lot of my early 1980s programming before I got reliable floppy discs.

So thank you for bringing back those memories.

[Mark Swift]

It turns out that getting images onto a QL platform for processing is a lot easier now than it was in 1990.
So I finally modded the HALFTONE program to display a P3 PPM image file.

HALFTONEp3.zip

(192.28 KiB) Downloaded 38 times

PPM is an uncompressed image format.
P3 PPM files are human readable, so pixel values are stored in ASCII format.
The files I used had one value per line for ease of processing. There's an example in the zip file above.

So primarily, the difference is structured vs random patterns? Is that then something that could be added to Photon to add additional options for converting JPEGs besides 25/50/75% dithering?

I'm not sure how half-toning compares to dithering.
It does seem to handle being viewed scaled down quite well as the MODE 256 screen grabs below show .

Thank you Mark. Nice programs.

Thanks Dilwyn, your post took me back.
Computer magazines, late night programming and dodgy media... good times.

[Maskenlos]

Anyway... I wondered... has anyone else written something similar?
i.e. odd, interesting but with no particular theme except time and effort.

Hi,

I remember there was something similar (same) as Halftone from Carlo Delhez around 1995. If not mistaken, the approach was to switch colour of a pixel in between 2 states to get a mix of it. I remember of some examples I have seen. Let me check my pile of discs later in January. Do not take this information as solid proven, it was 30 years ago.

Stephan

[BSJR]

Anyway... I wondered... has anyone else written something similar?
i.e. odd, interesting but with no particular theme except time and effort.

Hi,

I remember there was something similar (same) as Halftone from Carlo Delhez around 1995. If not mistaken, the approach was to switch colour of a pixel in between 2 states to get a mix of it. I remember of some examples I have seen. Let me check my pile of discs later in January. Do not take this information as solid proven, it was 30 years ago.

Stephan

It's on Dilwyn's site: https://dilwyn.theqlforum.com/graphics/engif.zip
It uses dithering and also works on higher resolutions than the standard QL.

BSJR

[dilwyn]

There was also something called Dithvide by Jan Polenicek (Omega) https://omega.webnode.page/productions-/

Dithvide Doom screen

08_doom.png (19.73 KiB) Viewed 1200 times

Dithvide picture of ball

[stevepoole]

Hi All,
The QL has 255 stipple 'colours', which can be used in place of mode 4 or 8....

But, Stipples only mix 2 colours out of 8, with horizontal, vertical or diagonal patterns.

By mixing 4 colours out of 8, we get far many more stipple colour mixes.

This is ok for PAPER background, but won't work with FILL....

Pity we can't use Talent's GraphiQL QDOS 'texture-fill' routine !

I will post the QL code after rummaging through old PC hard disks. Steve.

[tofro]

There was also something called Dithvide by Jan Polenicek (Omega) https://omega.webnode.page/productions-/

08_doom.png
15_ball.png

The Magnetic Scrolls Adventures can do the same in Mode 8

[stevepoole]

Hi Mark & All,
You put a lot of work into BigCHars_bas... and the visual result is excellent !
I like the way you avoid filling ARCs, but the method won't work on mixed backgrounds ?
Around 50 characters from the font are not treated, but your code does the job it was intended for well... Titles.
On QPC2 it is instantaneous, and provides an alternative to zoomed bitmap text.
Both codes were written in the '80s, when 4Mhz was rather slow for them !
No doubt other usefull programs had been written and abandoned for sluggishness ?