[HN Gopher] Lid - Lo-fi image dithering
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Lid - Lo-fi image dithering
Author : ecliptik
Score : 76 points
Date : 2023-01-12 19:11 UTC (3 hours ago)
(HTM) web link (rawtext.club)
(TXT) w3m dump (rawtext.club)
| xnx wrote:
| Recently: Pixel Accurate Atkinson Dithering for Images in HTML
| (32 comments) https://news.ycombinator.com/item?id=34052253
| khobragade wrote:
| Love these! Also check out Didder https://github.com/makeworld-
| the-better-one/didder https://vladh.net/dithering
| nilsb wrote:
| Didder is fantastic. I'm using it to convert images to
| grayscale for use with Waveshare e-ink displays. I've found no
| other tool that both lets you specify a custom palette (without
| which the resulting image looks pretty bad) and is reasonably
| quick.
|
| For future reference, this works beautifully with their 9.7"
| display: didder --palette '000000 111111 222222 333333 444444
| 555555 666666 777777 888888 999999 aaaaaa bbbbbb cccccc dddddd
| eeeeee ffffff' -g -i - -o - edm --serpentine FloydSteinberg
| sllabres wrote:
| Image Alchemy [1] Unfortunately not longer available. But one
| of the greatest image conversion software I know (including
| most of the here described algorithm for dithering and some
| more). And this feature set is from at least 25-30 years ago.
|
| I'm always getting a bit nostalgia when I see these dithered
| images and remember the time then with the fascination for
| the opposite direction: 'true color... wow that would be
| great' ;)
|
| [1] https://www.handmadesw.com/products/image_alchemy.htm
| phailhaus wrote:
| Beautiful! One suggestion: it would be helpful to put the
| original image first, so that people have context before seeing
| it dithered.
| danuker wrote:
| Error diffusion is by far my favorite. Works while zooming out
| also.
| guidoism wrote:
| It looks amazing. Honestly I'd rather see that in most books
| than colored pics.
| ethanwillis wrote:
| If you want to do dithering there are lots more
| variations(algorithms) on it with very very impressive results in
| the resulting quality.
| Kuraj wrote:
| FYI, the images on the website are shrunk by a small factor which
| messes up the dithering. They're best viewed in a new tab, or
| with the website zoomed to 125% on a 96dpi setting.
| rcthompson wrote:
| Yes, the scaling induces visual artifacts that pretty
| substantially misrepresent what each algorithm should look
| like. (In particular it adds vertical and horizontal bars that
| aren't on the actual image.) Definitely make sure you view the
| images at the proper zoom level.
| aliqot wrote:
| You'd think they'd have foreseen that and just cropped their
| examples to be pixel perfect for their own fixed width
| content column.
| AndrewStephens wrote:
| That doesn't work either, since browsers don't respect
| exact pixel sizes for elements even at 100% and at other
| zoom settings all bets are off.
|
| That is why I created this project[0], recently discussed
| here[1]
|
| [0] https://sheep.horse/2022/12/pixel_accurate_atkinson_dit
| herin...
|
| [1] https://news.ycombinator.com/item?id=34052253
| aliqot wrote:
| Doing the lord's work, thank you.
| tofof wrote:
| Yet another of many reasons in this thread for why dithering
| photographs for the web is stupid.
| fluoridation wrote:
| As has been pointed out by others before, while dithering is
| stylistic and useful for display in low color resolution screens,
| dithered images compress poorly. You'll almost always get more
| detail and color out of JPEG. At 30% quality I get a 43 KiB file,
| and the difference is much less noticeable than if I had tried to
| quantize down to two colors.
|
| Now, if the point is aesthetics and not efficiency, by all means
| use dithering.
| tedunangst wrote:
| In a sense, JPEG is fancy dithering. The DCT gives you a
| dithering pattern customized for exactly the image you're
| compressing, every dot placed to minimize error. (With some
| hand waving.)
| mikae1 wrote:
| ...and when you compare the size of JPEG with AVIF[1], dithered
| PNG may seem even more wasteful and pointless.
|
| [1] https://afontenot.github.io/image-formats-
| comparison/#abando...
| bob1029 wrote:
| > dithered images compress poorly
|
| If you think about error diffusion dithering in particular on a
| 1-bit palette - Information theory dictates that you are kind
| of pushing entropy limits as-is. Compression is still possible,
| but to get any kind of realistic gain it's going to have to be
| slow compression.
|
| Piping stuff like 1-bit dithered graphics through fast, lossy
| JPEG/MPEG-style compressors (i.e. quantized DCT) will yield
| absolute garbage results.
| jarenmf wrote:
| Could you please elaborate on the link of error diffusion to
| information theory? as far as I understand error diffusion
| minimizes the quantization error for lower frequencies on the
| expense of adding more noise to higher frequencies. i.e it
| seems to be only optimizing for human perception
| bob1029 wrote:
| You're right - in pure information theoretic terms there is
| nothing special happening here. It's a tradeoff like
| always. But, in human perceptual terms (i.e. how JPEG/MPEG
| are designed), you may find substantial gain in _useful_
| information per bit by applying dithering.
|
| The useful amount of information represented by any given
| bit of data is much larger in this arrangement. 1 bit = 1
| entire pixel. In other schemes, you have upwards of 24 bits
| representing the contents of 1 pixel. To human eyes, only 8
| of these bits _really_ matter. You can usually throw away
| 50% of the other 16 without anyone noticing.
| sprash wrote:
| This is interesting if you are after retro effects. State of the
| art dithering however works with blue noise threshold textures[1]
| because we have plenty of memory available these days. Here is a
| nice comparison of all kinds of dithering algorithms that also
| shows the clear superiority of blue noise dithering: [2].
|
| 1.: http://momentsingraphics.de/BlueNoise.html
|
| 2.: https://surma.dev/things/ditherpunk/
| somat wrote:
| A good forum post on the challenges of the "obra dinn" dither
| effect in 3d.
|
| https://forums.tigsource.com/index.php?topic=40832.msg136374...
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