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Author Topic: Image processing for Norwegian pixel
daveo
Newbie
Posts: 12
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Post Image processing for Norwegian pixel
on: October 13, 2020, 10:57
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Hi Sandy.
Thank you for the many hours of enjoyment I have had playing with my Polargraph.
I really like the Norwegian pixel style but my results are a bit hit and miss.
I think it may be I'm not processing the images sufficiently to suit the format.
Can you give me any advice on how to tweak the images to get the best results. I use Gimp.
I typically set amplitude to 15 and leave the wavelength at 2
Regards
Dave

Leopain
Newbie
Posts: 2
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Leopain
Post Re: Image processing for Norwegian pixel
on: October 13, 2020, 11:59
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Hi there.
I am 62 and have download the software but have no idea how to open it. Do you not have a windows base version please.

sandy
Administrator
Posts: 1448
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sandy
Post Re: Image processing for Norwegian pixel
on: October 13, 2020, 12:53
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DaveO - I wonder if you're bumping into issues about file formats. What actually happens? Although the machine looks for PBM files, it's actually PGM format that needs to be inside it. PGM is greyscale whereas PBM _might_ be greyscale - but it also might be an indexed colour format.

Greyscale doesn't do any encoding, that it, the value of a pixel at a position is interpreted as the greyness of the pixel itself. If it has the value of 128 then it's mid-grey (255 is white, 0 is black).

The same pixel value with an indexed colour file actually points to "colour entry 128 in a palette of colours in the file", so could be anything because that palette is arbitrary. The actual colour specified at 128 might black or white (or green or red...).

I haven't done a thorough investigation of it (and actually haven't used it myself for years so GIMP might be different now), but I remember that GIMP used to save PBM files as indexed colours and I needed to specifically ask it to export as PGM to force it to use greyscales. PGM/PBM are such old file formats that nobody knows how to use them anymore so I wish I could have just loaded JPEGs or GIFs or PNGs but tbh I couldn't face building an image parser that would do that in a memory efficient way! PBM has the benefit of being dead simple.

http://www.polargraph.co.uk/2012/08/norwegian-pixel/

Leopain: There is no age restriction in the software! Have you followed the guide at https://www.instructables.com/Polargraph-Drawing-Machine/?

sn

daveo
Newbie
Posts: 12
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Post Re: Image processing for Norwegian pixel
on: October 14, 2020, 06:39
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I guess I didn't express my problem correctly.
I don't have a problem getting my Polargraph to draw the images , it does that fine.
It's that I don't get the sort of definition/contrast I am hoping for.
The image you used when describing Norwegian pixel on August 12 2012 had excellent contrast , was it just the fact that the image suited Norwegian format well or did you adjust brightness/contrast to suit.
It looks like you used wavelength 1 ? , I typically don't do that as it can take 15-18 hours to draw an largeish image.

sandy
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Posts: 1448
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sandy
Post Re: Image processing for Norwegian pixel
on: October 14, 2020, 21:10
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Ah right, got you. I don't remember doing anything special, but the most recent drawings I did using this style were all too faint - now you mention it.

So they look overexposed, too much paper and not enough ink. Now like I say, I didn't do anything special first, I was probably just lucky. Now, I think I would compress the image so that it was as dark as I could make it and still see it. You're right that I used the smallest wavelength I could, and yes, it too a long time.

With wavelength: 2 will potentially put a space inbetween each line, so I think I would choose a thicker pen to use that with so that the ink fills in the gap.

I drew this one ages back
Unsavoury character Norwegian pixel polargraph drawing

based on
Andrea Laudano

and don't imagine I would have done any compression on that so you can see the difference between the original and the copy. I re-read my description - it took 3 days!

sn

daveo
Newbie
Posts: 12
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Post Re: Image processing for Norwegian pixel
on: October 18, 2020, 11:44
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Thanks Sandy
I might start taking photos with my camera instead of iPhone so I have control over how things come out.
3 days ? You are patient

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