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Offer of assistance to frustrated Rastaconverters


I have now had quite a lot of practice at editing the Rasta kernel to remove the kind of 'line artefacts' produced by the well-known player-repositioning bug (these manifest themselves as a short (often broken) horizontal line of an obviously wrong colour somewhere in the xex image-one that doesn't appear in the corresponding png image output).


If anyone is frustrated by one of these artefacts stubbornly appearing in an otherwise great conversion, I am happy to try to remove it for you. Note that running the conversion on further for some time with 'Restart stopped conversion' often causes them to disappear without further intervention.


To take advantage of this offer, you would need to PM me the following files from Rastaconverter's 'Generator' folder, extracted immediately after generating the faulty xex:


output.png.rp        (=the main kernel program)

output.png.rp.ini   (=the kernel initiation header)

output.png.mic      (=the bitmap image)

output.png.pmg     (=the player/missile data)


For anyone keen to do some DIY for this, the problem arises when the kernel attempts to reposition a player to a horizontal position such that the player's left edge would be displayed within a 5 colour clock window after the write to HPOSPx completes.  Rastaconverter assumes such players display at the assigned position, with priority over background pixels. In fact, the player is not triggered for display at all on that scanline, so any background pixels intended to be 'covered' by said player are displayed instead- the 'incorrect' colour seen in the artefact represents these background pixels 'showing through'.


The solution is usually to reprogram the kernel to avoid a HPOSPx write completing within the critical 5 colour clock window before the player is displayed.  This can be very easy or very tricky depending on what other critically-timed instructions fall in the vicinity.  Occasionally the only simple way out is to edit the bitmap and/or the player missile data to cover up the offending pixels with either a playfield colour or another player colour.  Obviously, how good a solution that kludge turns out to be depends on how critical these pixels being the colour Rastaconverter originally intended is to the image...

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Tutorial For Correction Of Rastaconverter Line Artefacts


14 hours ago, ivop said:

@drpeter, without quoting your lengthy and informative post, how do  you find the offending line in the 240 line kernel? I tried it once or twice, but it took me quite some time. I replaced the instructions by NOPs if I recall correctly.



I have put together a detailed walkthrough tutorial (attached) for anyone wishing to tackle correcting artefacts themselves


Tutorial Walkthrough.zip

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Sir Ian McKellen plays the wizard Gandalf in Peter Jackson's movie trilogy of the  fantasy novel 'The Lord Of The Rings' byJRR Tolkien.


Frodo: 'I wish the Ring had never come to me. I wish none of this had happened.'
Gandalf: 'So do all who live to see such times, but that is not for them to decide. All we have to decide is what to do with the time that is given to us. '


37 colours





Edited by drpeter
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If I am not wrong I forgot to post my NewTek Demo here. It was included in NYD 2020.


I ripped, manually edited and converted some images from the famous Amiga NewTek Demo Reel #1 (1987).

I added to the video original demo Art of Noise's Paranoimia music, it isn't included in the Atari demo.



Newtek00.png.f5a199c0034c45217127e84b8e7a949c.png Newtek01.png.e7c450b893eb409ee22e0f074a65d60c.png Newtek02.png.b3de617eb4d7fbb25cb141e4b82065c3.png


Newtek03.png.9e90b12b2fc97fc11247438e8ee325f4.png Newtek04.png.d6308e20e1c55f6e58be4599512e179e.png Newtek05.png.be94ff3b8c749bc4833bcd7d365bdd54.png


Newtek06.png.8f7d037c224245935eb5b3137545e95e.png Newtek07.png.74e2ce636e9886bf780d24bbd36ea44e.png Newtek08.png.472fb55d466fc21f5c2e5911151ad938.png


Newtek09.png.24c103ce636b213e803fb3ad31d1a770.png Newtek10.png.5901de5d3dcc78dd255d26c5600a29d9.png Newtek11.png.3e7f97bcf5866cca01e8caced115e443.png


You can download the demo here: https://atariage.com/forums/topic/298221-nyd-2020/?do=findComment&comment=4441757



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This one is quite stunning.

19 hours ago, amarok said:

Meiringen-Hasliberg cable car, Switzerland. 75 colors.




amarok_cable_car.xex 22.15 kB · 12 downloads

This one is actually quite stunning, the more I look the more I like it.

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On 11/17/2020 at 10:40 AM, drpeter said:

Wow. Just Wow.  Absolutely gorgeous.

This has to be among my all-time favourite Rasta images!

Yeah, it almost looks like it has been pixelated by hand on a far more capable machine!

40 minutes ago, Gunstar said:

This one is actually quite stunning, the more I look the more I like it.

I like it how different "converters" have their own style. drpeter, you, amarok, one can almost determine who did the conversion without looking at the name. This one is typical amarok, and I like it, too!

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'The Repository' is a zoom-in and crop from a much higher resolution and vast fantasy landscape image from The Elder Scrolls universe. The original image when reduced had far too little detail on distant objects in the much larger panoramic view. So I decided to zoom in on certain areas of interest or focal points to capture much more detail of, in this case, my self-named 'Repository' as I wasn't sure exactly what type of structure it is supposed to be and made an educated guess from my art history studies in college and this type of Greco-Roman architecture. I'll probably do a few more close-ups of other areas in the original image, as the original artwork is fabulous anyway in piece or whole.


My next conversion that is running right now is another Amiga color-cycle image 'Deep Forest' that has 147 colors in the seasonal/time-of-day setting I chose. I did much more pre-processing  to it than I usually do to my usual Rasta images with gamma, contrast, brightness and saturation for maximum color transition after attempting unsatisfactory results with no pre-processing several times. It looks promising so far, but it's only at about 100 million evaluations at this point and some ways to go yet on reducing the normal distance.

Edited by Gunstar
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