20 ms·

A Pixel Is Not a Little Square (1995) [pdf]

81 points by noch 6y ago

kalal 6y ago
This is important point indeed. Here is what helps myself, when thinking about pixels. - pixels are point samples in 2D space - their position is exact - position of of top-left point is (0,0) - position of bottom right is (cols-1,rows-1) This way all math work (subsampling, affine or perspective warps, lens distortion, or even warping between image and any layer neural network). Failure to do that, will cause subtle issues that will degrade your performance. These will become quite important when working with pixel accurate methods (3d object tracking, object detection in tiny resolutions and 1-1 mapping between OpenGL and Neural Network). So I have to agree, pixels are not tiny squares, they are dots in 2d space.
pixlartthrowway 6y ago
As a pixel art artist, I certainly see pixels as little squares. As a 3D programmer working with 2D point-sample textures, I do not see pixels as little squares. So the answer to whether or not a pixel is a little square is, like so many of life's questions, not a simple yes or no, but rather, it depends.
- astrange 6y ago
  Pixel art is a kind of fake aesthetic based on what NES emulators show games as, though. In real life they were made to go through various filters that blurred the image until it didn't look as much like little squares.
  - boomlinde 6y ago
    That's just one example, a game console where the video output was typically via composite video or even an RF modulator to a TV. Not so much with e.g. VGA mode 0x13 PC graphics on a relatively crisp computer display.
    - kragen 6y ago
      VGA mode 13h PC graphics on a relatively crisp computer CRT display still drew each of its 200 "scan lines" as a double fuzzy line, and a single pixel on it as a double fuzzy dot (more or less an isotropic Gaussian, despite what Smith says) or a double fuzzy dash. Superimposed on these fuzzy patterns you had the shadow-mask circular colored dots or the Trinitron colored rectangles. Sometimes you would also get echos or "ghosting", if there was an impedance mismatch or two in the analog signal path. Later graphics cards in the 01990s would sometimes emulate CGA 320×200 and mode 13h by using more scan lines, giving pixels that looked more like little squares. Or, well, rectangles.
      - boomlinde 6y ago
        > VGA mode 13h PC graphics on a relatively crisp computer CRT display still drew each of its 200 "scan lines" as a double fuzzy line, and a single pixel on it as a double fuzzy dot (more or less an isotropic Gaussian, despite what Smith says) or a double fuzzy dash. Superimposed on these fuzzy patterns you had the shadow-mask circular colored dots or the Trinitron colored rectangles. Now we're veering back into technical details of its implementation. The question is, is "squares" (well, yes, rectangles) a useful model of what is visible to the viewer? To that end, the fact that each line was traced as twice on the display is trivial. We have to concern ourselves with the visible result to answer that question I have a decent CRT VGA monitor here, connected to a VGA card in an old PC, and at lower resolutions the pixels are crisp and hard. The monitors are made for reading at a higher resolution after all. If I press my face at the screen I can see that yes, the pixels appear on a much more fine-grained grid of apertures, and yes, this and other factors somewhat fuzz their boundaries. But for normal use at an arm's length, rectangles are a very good approximate model for some display types that were in use while VGA was still a thing games used, one that a skilled artist can exploit in an entirely different way than they'd exploit the characteristics of NTSC/PAL displays or an RGB display with a coarser dot pitch.
        kragen 6y ago
        A rectangle is a pretty reasonable approximation of a fuzzy point. It's an even more reasonable approximation of two fuzzy parallel dashes.
- ogurechny 6y ago
  That's quite alarming. On many systems with TV output, including widely popular consoles, there were no pixels at all, just an analog line signal, most often modulated/composited/combined, and often low in quality because of cost-effective hardware and cables. Artists certainly looked at how images appeared on TV screens, and not at raw values of the bitmap samples presented as squares, and they compensated for unwanted effects. It is slightly maddening to know that the lack of analog output emulation in early console emulators and general lack of education resulted in the modern faux-retro aesthetic, some kind of new age belief that pixels should be big blocks. Mario sprite was never intended to be seen as made of blocks, no matter how many times people use that scaled abomination. You do have big flat pixels when you have high quality but low physical DPI output device. Say, black and white Macintosh, or late '90s computer monitors displaying '80s screen resolutions, or a panel of individual LEDs. On the other hand, halftones are also sharp and have low DPI, but have no square grid at all, nor they correspond to source data used in printing in any straightforward way. To conclude, big flat rectangles are just a specific artistic choice, they are not universal at all.
  - jcelerier 6y ago
    > Mario sprite was never intended to be seen as made of blocks idk I still play on a 1990s CRT and it's pretty blocky
  - mrob 6y ago
    >Mario sprite was never intended to be seen as made of blocks It was depicted as made of blocks on most versions of the cover art: https://www.mobygames.com/game/super-mario-bros/cover-art https://www.mobygames.com/game/super-mario-bros/cover-art And many Mario games were released for portable systems with sharp LCD screens, and they used the same pixel art techniques.
    - ogurechny 6y ago
      Oh god, they even turned it at arbitrary angle, like in some teenage Flash animation.
- virtualritz 6y ago
  > As a pixel art artist, I certainly see pixels as little squares. Then you are ignorant about the history of pixel art. Which I am not judging btw. Just saying. Pixel art from the golden years doesn't look right when displayed as little squares. It needs to be shown on a CRT or with an overlay emulating this look to do its creator's intentions justice. "The Bitmap Brothers: Universe" (fantastic book btw.) went to great lengths to replicate the original rendering of the depicted pixel art. See e.g. [0]. [0] https://twitter.com/romvg/status/776081029882937344 https://twitter.com/romvg/status/776081029882937344
  - nearbuy 6y ago
    Funny to think we're nostalgic for something that didn't really exist.
  - crazygringo 6y ago
    This is a bit of a misunderstood overreaction. It's true that if you were playing Super Mario on your TV, the normal experience was for it to be a bit blurry. On the other hand, if you were playing Lemmings on an Apple monitor with Sony Trinitron technology, the pixels were exceptionally clear. Here's what Trinitron looked like: https://ancientelectronics.files.wordpress.com/2013/01/svidsg.jpg https://ancientelectronics.files.wordpress.com/2013/01/svids... I'd argue that playing Lemmings in an emulator, you want the pixels to be clear, without a CRT overlay -- that this would be closer to the artists' intentions.
  - pixlartthrowway 6y ago
    Some pixel artists indeed intended their creations to be seen as little squares, even if CRTs of the 1980s stretched the squares into rectangles and fuzzed and scan-lined them. Right now there is a story on HN about a $660,000 copy of Super Mario Brothers. Look closely at Nintendo's original 1980s box art. Mario is made up of crisp little "pixel perfect" squares: https://en.wikipedia.org/wiki/Super_Mario_Bros.#/media/File:Super_Mario_Bros._box.png https://en.wikipedia.org/wiki/Super_Mario_Bros.#/media/File:... Look at other Nintendo pixel box art from the 1980s. Many of the earliest Nintendo games had this common box art style. It's all little squares: https://en.wikipedia.org/wiki/Metroid_(video_game)#/media/File:Metroid_boxart.jpg https://en.wikipedia.org/wiki/Metroid_(video_game)#/media/Fi... https://www.oldschoolgamermagazine.com/early-nes-nintendo-box-art-pt-1-black-box-titles/ https://www.oldschoolgamermagazine.com/early-nes-nintendo-bo... I have an NES classic edition and it lets you select if you want the CRT effect applied or not. Sometimes I play with this effect applied (how I experienced it as a child) but other times I enjoy the "pixel perfect" mode. I designed pixel fonts back in the 1990s and I was always unhappy about how CRTs fuzzed them. I loved the sharp little squares of LCDs much better.
im3w1l 6y ago
I can't help but think of the famous humpty dumpty quote > When I use a word," Humpty Dumpty said, in rather a scornful tone, "it means just what I choose it to mean—neither more nor less." "The question is," said Alice, "whether you can make words mean so many different things." "The question is," said Humpty Dumpty, "which is to be master—that's all." The fact is that pixels don't have a well defined meaning. Some people use them as squares, some people use them as samples. Then you get into subpixel font rendering, where you quite explicitly acknowledge the screen as master, and you design your image for a desired result. So yeah it's an ecosystem of people doing different things with different interpretations, and trying to mostly play nice with each other.
salamanderman 5y ago
DLP is little squares
topiolli 5y ago
Pixels, at least when they come from cameras or need to be mapped to a 3D world, are still not square. https://doc.visionappster.com/3.0-beta5/engine/world-coordinates/#pixels https://doc.visionappster.com/3.0-beta5/engine/world-coordin...
jsnell 6y ago
(1995). Previous discussion: https://news.ycombinator.com/item?id=8614159 https://news.ycombinator.com/item?id=8614159 https://news.ycombinator.com/item?id=20535984 https://news.ycombinator.com/item?id=20535984
- posobin 6y ago
  Plus there are 12 comments on HN mentioning this URL in 12 different discussions: https://ampie.app/url-context?url=alvyray.com/Memos/CG/Microsoft/6_pixel.pdf https://ampie.app/url-context?url=alvyray.com/Memos/CG/Micro..., and it has been linked from this great article on alpha compositing by Bartosz Ciechanowski (you should really check out his blog if you haven't seen it): https://ciechanow.ski/alpha-compositing/ https://ciechanow.ski/alpha-compositing/
- dang 6y ago
  Also https://news.ycombinator.com/item?id=1472175 https://news.ycombinator.com/item?id=1472175 - June 2010 (20 comments)
Applejinx 6y ago
Indeed… and a sample is not a point along the audio waveform :)
- pianom4n 6y ago
  Don't you have that backwards? A sample _is_ a point along along a waveform. https://youtu.be/cIQ9IXSUzuM?t=359 https://youtu.be/cIQ9IXSUzuM?t=359
  - steerablesafe 6y ago
    A sample is a point along the band-limited waveform (otherwise you get aliasing). If you treat band-limiting and sampling as a single operation on the original waveform then it's integrating over neighboring points on the waveform with some kind of kernel, the shape of the kernel depends on the form of the band limiting.
    - Applejinx 6y ago
      A sample is a mathematical value akin to the handle of a Bezier curve, there to facilitate the reconstruction of a different waveform that may have little to do with the sample's apparent position at all. :) (granted, this is specifically at high frequencies: at low enough frequencies, the sample might as well be the waveform within whatever contstraints the word length puts on you)
  - marcosdumay 6y ago
    On the digital wave, yes (that's the definition of a sample, or of the wave). On the analogical wave, no.
    - kragen 6y ago
      (In English the word is "analog" or "analogue.")
    - aidenn0 6y ago
      As analogical waves don't have a concept of samples, I'm not sure what your point is?
potatoman22 6y ago
I wish the abstract actually summarized her points.
- packetslave 6y ago
  Alvy Ray Smith, founder of Pixar, is not a "her"
  - potatoman22 6y ago
    That's neat, but I stand by my point.
Ono-Sendai 6y ago
It's more like a little fuzzy blob, typically with RGB sub-blobs.
- kennywinker 6y ago
  I think you're thinking of a pixel on a display? Because arguably that's just a rendering of a data set. The pixels the article are referring to are the data set, a set of point samples. In which case it has no shape - since it's a point - and the r, g and b components are just different samples at the same point
- edrxty 6y ago
  This is where I take issue with the paper. The sub blobs are really important because different displays/focal plane arrays have different pixel arrangements that can be dramatically different. You can't assume it'll be a collection of three sub-elements (often there will be different ratios in a complex arrangement) or that the pixel is even being displayed as RGB (CMY?). You have to know some things about your pixel arrangements in order to properly anti-alias, font render, or display camera images, otherwise the result can be pretty ugly.
- dhosek 6y ago
  Back when I was writing code for the Apple ][ (long-hand, on graph paper), I worked out graphics layouts by drawing my pixels four to a square on the graph paper, representing each pixel with a circle. I also never forgot that (a) the pixels were actually kind of rectangular and (2) in hires graphics mode, if you viewed things as 280x192, adjacent pixels were either •• and • or • and •• depending on the high bit of the byte that had the bitmap data. I think it might have been possible to get •◦• where one RGB-triple was split across bytes.
- jayd16 6y ago
  Not exactly right either. Before its displayed to some approximation in some RGB array, it was some back buffer. That back buffer could have been attempting to render an infinitely small, crisp line or a line almost two pixels wide. The point is that kind of information is not encoded in the buffer. Its just a point sample of the output of the previous stage in the pipeline.
deleted 6y ago
[deleted]
crazygringo 6y ago
Is this not outdated? It uses examples of how pixels on scanners, printers, and CRT monitors are not squares. Fair enough. Back when this was written, one could very reasonably argue that pixels were intended to be point samples with a convolution. But modern pixels on most LCD screens certainly are exceedingly crisp squares (with subpixels), and processing RAW camera sensor data, antialiasing techniques, and image resampling seems to "mostly" assume that pixels do represent the average color over a square rather than a point sample. Not perfectly, but as a reasonable first-order approximation. I understand that 25 years ago it might have been reasonable to argue that pixels aren't squares. But today... aren't they, at least as a first-order approximation? (With some further adjustments to avoid antialiasing artifacts, desired sharpness, and so forth.) The idea that pixels are primarily point samples seems far more misleading -- as if they were analagous to audio samples which are point samples as a first-order approximation, but pixels are nothing like audio samples.
- 3dee 6y ago
  They are exactly like audio point samples. Pixels are always interpolated, just like audio. The fact that 1080 pixels exactly fit 1080 screen pixels don't give pixels a shape. And by the way, most modern display pixels are not squares. They come in all kinds of shapes. Triangles for example.
- skavi 6y ago
  The AMOLED displays in most higher end phones definitely do not have square pixels.
  - ksec 6y ago
    I think you mean Pentile Sub pixel. The Pixel itself are still square.
    - numpad0 6y ago
      Pixel itself are like ////// and not square
- 6y ago
acomjean 6y ago
One of the weird experiences I had in college was working for the paper in the 90s. We has desktop publishing but the photos for the paper were taken out back to a machine with a screen copied them into solid black dots of various sizes. They were waxed onto printed newspaper pages and wisked off to the printer. I often wondered how you would reproduce it digitally but apparently I was thinking about it wrong. Halftone is the term https://en.m.wikipedia.org/wiki/Halftone https://en.m.wikipedia.org/wiki/Halftone

81 points by noch 6y ago

This is important point indeed. Here is what helps myself, when thinking about pixels. - pixels are point samples in 2D space - their position is exact - position of of top-left point is (0,0) - position of bottom right is (cols-1,rows-1) This way all math work (subsampling, affine or perspective warps, lens distortion, or even warping between image and any layer neural network). Failure to do that, will cause subtle issues that will degrade your performance. These will become quite important when working with pixel accurate methods (3d object tracking, object detection in tiny resolutions and 1-1 mapping between OpenGL and Neural Network). So I have to agree, pixels are not tiny squares, they are dots in 2d space.

pixlartthrowway 6y ago

As a pixel art artist, I certainly see pixels as little squares. As a 3D programmer working with 2D point-sample textures, I do not see pixels as little squares. So the answer to whether or not a pixel is a little square is, like so many of life's questions, not a simple yes or no, but rather, it depends.

astrange 6y ago
Pixel art is a kind of fake aesthetic based on what NES emulators show games as, though. In real life they were made to go through various filters that blurred the image until it didn't look as much like little squares.
- boomlinde 6y ago
  That's just one example, a game console where the video output was typically via composite video or even an RF modulator to a TV. Not so much with e.g. VGA mode 0x13 PC graphics on a relatively crisp computer display.
  - kragen 6y ago
    VGA mode 13h PC graphics on a relatively crisp computer CRT display still drew each of its 200 "scan lines" as a double fuzzy line, and a single pixel on it as a double fuzzy dot (more or less an isotropic Gaussian, despite what Smith says) or a double fuzzy dash. Superimposed on these fuzzy patterns you had the shadow-mask circular colored dots or the Trinitron colored rectangles. Sometimes you would also get echos or "ghosting", if there was an impedance mismatch or two in the analog signal path. Later graphics cards in the 01990s would sometimes emulate CGA 320×200 and mode 13h by using more scan lines, giving pixels that looked more like little squares. Or, well, rectangles.
    - boomlinde 6y ago
      > VGA mode 13h PC graphics on a relatively crisp computer CRT display still drew each of its 200 "scan lines" as a double fuzzy line, and a single pixel on it as a double fuzzy dot (more or less an isotropic Gaussian, despite what Smith says) or a double fuzzy dash. Superimposed on these fuzzy patterns you had the shadow-mask circular colored dots or the Trinitron colored rectangles. Now we're veering back into technical details of its implementation. The question is, is "squares" (well, yes, rectangles) a useful model of what is visible to the viewer? To that end, the fact that each line was traced as twice on the display is trivial. We have to concern ourselves with the visible result to answer that question I have a decent CRT VGA monitor here, connected to a VGA card in an old PC, and at lower resolutions the pixels are crisp and hard. The monitors are made for reading at a higher resolution after all. If I press my face at the screen I can see that yes, the pixels appear on a much more fine-grained grid of apertures, and yes, this and other factors somewhat fuzz their boundaries. But for normal use at an arm's length, rectangles are a very good approximate model for some display types that were in use while VGA was still a thing games used, one that a skilled artist can exploit in an entirely different way than they'd exploit the characteristics of NTSC/PAL displays or an RGB display with a coarser dot pitch.
      - kragen 6y ago
        A rectangle is a pretty reasonable approximation of a fuzzy point. It's an even more reasonable approximation of two fuzzy parallel dashes.
ogurechny 6y ago
That's quite alarming. On many systems with TV output, including widely popular consoles, there were no pixels at all, just an analog line signal, most often modulated/composited/combined, and often low in quality because of cost-effective hardware and cables. Artists certainly looked at how images appeared on TV screens, and not at raw values of the bitmap samples presented as squares, and they compensated for unwanted effects. It is slightly maddening to know that the lack of analog output emulation in early console emulators and general lack of education resulted in the modern faux-retro aesthetic, some kind of new age belief that pixels should be big blocks. Mario sprite was never intended to be seen as made of blocks, no matter how many times people use that scaled abomination. You do have big flat pixels when you have high quality but low physical DPI output device. Say, black and white Macintosh, or late '90s computer monitors displaying '80s screen resolutions, or a panel of individual LEDs. On the other hand, halftones are also sharp and have low DPI, but have no square grid at all, nor they correspond to source data used in printing in any straightforward way. To conclude, big flat rectangles are just a specific artistic choice, they are not universal at all.
- jcelerier 6y ago
  > Mario sprite was never intended to be seen as made of blocks idk I still play on a 1990s CRT and it's pretty blocky
- mrob 6y ago
  >Mario sprite was never intended to be seen as made of blocks It was depicted as made of blocks on most versions of the cover art: https://www.mobygames.com/game/super-mario-bros/cover-art https://www.mobygames.com/game/super-mario-bros/cover-art And many Mario games were released for portable systems with sharp LCD screens, and they used the same pixel art techniques.
  - ogurechny 6y ago
    Oh god, they even turned it at arbitrary angle, like in some teenage Flash animation.
virtualritz 6y ago
> As a pixel art artist, I certainly see pixels as little squares. Then you are ignorant about the history of pixel art. Which I am not judging btw. Just saying. Pixel art from the golden years doesn't look right when displayed as little squares. It needs to be shown on a CRT or with an overlay emulating this look to do its creator's intentions justice. "The Bitmap Brothers: Universe" (fantastic book btw.) went to great lengths to replicate the original rendering of the depicted pixel art. See e.g. [0]. [0] https://twitter.com/romvg/status/776081029882937344 https://twitter.com/romvg/status/776081029882937344
- nearbuy 6y ago
  Funny to think we're nostalgic for something that didn't really exist.
- crazygringo 6y ago
  This is a bit of a misunderstood overreaction. It's true that if you were playing Super Mario on your TV, the normal experience was for it to be a bit blurry. On the other hand, if you were playing Lemmings on an Apple monitor with Sony Trinitron technology, the pixels were exceptionally clear. Here's what Trinitron looked like: https://ancientelectronics.files.wordpress.com/2013/01/svidsg.jpg https://ancientelectronics.files.wordpress.com/2013/01/svids... I'd argue that playing Lemmings in an emulator, you want the pixels to be clear, without a CRT overlay -- that this would be closer to the artists' intentions.
- pixlartthrowway 6y ago
  Some pixel artists indeed intended their creations to be seen as little squares, even if CRTs of the 1980s stretched the squares into rectangles and fuzzed and scan-lined them. Right now there is a story on HN about a $660,000 copy of Super Mario Brothers. Look closely at Nintendo's original 1980s box art. Mario is made up of crisp little "pixel perfect" squares: https://en.wikipedia.org/wiki/Super_Mario_Bros.#/media/File:Super_Mario_Bros._box.png https://en.wikipedia.org/wiki/Super_Mario_Bros.#/media/File:... Look at other Nintendo pixel box art from the 1980s. Many of the earliest Nintendo games had this common box art style. It's all little squares: https://en.wikipedia.org/wiki/Metroid_(video_game)#/media/File:Metroid_boxart.jpg https://en.wikipedia.org/wiki/Metroid_(video_game)#/media/Fi... https://www.oldschoolgamermagazine.com/early-nes-nintendo-box-art-pt-1-black-box-titles/ https://www.oldschoolgamermagazine.com/early-nes-nintendo-bo... I have an NES classic edition and it lets you select if you want the CRT effect applied or not. Sometimes I play with this effect applied (how I experienced it as a child) but other times I enjoy the "pixel perfect" mode. I designed pixel fonts back in the 1990s and I was always unhappy about how CRTs fuzzed them. I loved the sharp little squares of LCDs much better.

im3w1l 6y ago

I can't help but think of the famous humpty dumpty quote > When I use a word," Humpty Dumpty said, in rather a scornful tone, "it means just what I choose it to mean—neither more nor less." "The question is," said Alice, "whether you can make words mean so many different things." "The question is," said Humpty Dumpty, "which is to be master—that's all." The fact is that pixels don't have a well defined meaning. Some people use them as squares, some people use them as samples. Then you get into subpixel font rendering, where you quite explicitly acknowledge the screen as master, and you design your image for a desired result. So yeah it's an ecosystem of people doing different things with different interpretations, and trying to mostly play nice with each other.

salamanderman 5y ago

DLP is little squares

topiolli 5y ago

Pixels, at least when they come from cameras or need to be mapped to a 3D world, are still not square. https://doc.visionappster.com/3.0-beta5/engine/world-coordinates/#pixels https://doc.visionappster.com/3.0-beta5/engine/world-coordin...

jsnell 6y ago

(1995). Previous discussion: https://news.ycombinator.com/item?id=8614159 https://news.ycombinator.com/item?id=8614159 https://news.ycombinator.com/item?id=20535984 https://news.ycombinator.com/item?id=20535984

posobin 6y ago
Plus there are 12 comments on HN mentioning this URL in 12 different discussions: https://ampie.app/url-context?url=alvyray.com/Memos/CG/Microsoft/6_pixel.pdf https://ampie.app/url-context?url=alvyray.com/Memos/CG/Micro..., and it has been linked from this great article on alpha compositing by Bartosz Ciechanowski (you should really check out his blog if you haven't seen it): https://ciechanow.ski/alpha-compositing/ https://ciechanow.ski/alpha-compositing/
dang 6y ago
Also https://news.ycombinator.com/item?id=1472175 https://news.ycombinator.com/item?id=1472175 - June 2010 (20 comments)

Applejinx 6y ago

Indeed… and a sample is not a point along the audio waveform :)

pianom4n 6y ago
Don't you have that backwards? A sample _is_ a point along along a waveform. https://youtu.be/cIQ9IXSUzuM?t=359 https://youtu.be/cIQ9IXSUzuM?t=359
- steerablesafe 6y ago
  A sample is a point along the band-limited waveform (otherwise you get aliasing). If you treat band-limiting and sampling as a single operation on the original waveform then it's integrating over neighboring points on the waveform with some kind of kernel, the shape of the kernel depends on the form of the band limiting.
  - Applejinx 6y ago
    A sample is a mathematical value akin to the handle of a Bezier curve, there to facilitate the reconstruction of a different waveform that may have little to do with the sample's apparent position at all. :) (granted, this is specifically at high frequencies: at low enough frequencies, the sample might as well be the waveform within whatever contstraints the word length puts on you)
- marcosdumay 6y ago
  On the digital wave, yes (that's the definition of a sample, or of the wave). On the analogical wave, no.
  - kragen 6y ago
    (In English the word is "analog" or "analogue.")
  - aidenn0 6y ago
    As analogical waves don't have a concept of samples, I'm not sure what your point is?

potatoman22 6y ago

I wish the abstract actually summarized her points.

packetslave 6y ago
Alvy Ray Smith, founder of Pixar, is not a "her"
- potatoman22 6y ago
  That's neat, but I stand by my point.

Ono-Sendai 6y ago

It's more like a little fuzzy blob, typically with RGB sub-blobs.

kennywinker 6y ago
I think you're thinking of a pixel on a display? Because arguably that's just a rendering of a data set. The pixels the article are referring to are the data set, a set of point samples. In which case it has no shape - since it's a point - and the r, g and b components are just different samples at the same point
edrxty 6y ago
This is where I take issue with the paper. The sub blobs are really important because different displays/focal plane arrays have different pixel arrangements that can be dramatically different. You can't assume it'll be a collection of three sub-elements (often there will be different ratios in a complex arrangement) or that the pixel is even being displayed as RGB (CMY?). You have to know some things about your pixel arrangements in order to properly anti-alias, font render, or display camera images, otherwise the result can be pretty ugly.
dhosek 6y ago
Back when I was writing code for the Apple ][ (long-hand, on graph paper), I worked out graphics layouts by drawing my pixels four to a square on the graph paper, representing each pixel with a circle. I also never forgot that (a) the pixels were actually kind of rectangular and (2) in hires graphics mode, if you viewed things as 280x192, adjacent pixels were either •• and • or • and •• depending on the high bit of the byte that had the bitmap data. I think it might have been possible to get •◦• where one RGB-triple was split across bytes.
jayd16 6y ago
Not exactly right either. Before its displayed to some approximation in some RGB array, it was some back buffer. That back buffer could have been attempting to render an infinitely small, crisp line or a line almost two pixels wide. The point is that kind of information is not encoded in the buffer. Its just a point sample of the output of the previous stage in the pipeline.

deleted 6y ago

[deleted]

crazygringo 6y ago

Is this not outdated? It uses examples of how pixels on scanners, printers, and CRT monitors are not squares. Fair enough. Back when this was written, one could very reasonably argue that pixels were intended to be point samples with a convolution. But modern pixels on most LCD screens certainly are exceedingly crisp squares (with subpixels), and processing RAW camera sensor data, antialiasing techniques, and image resampling seems to "mostly" assume that pixels do represent the average color over a square rather than a point sample. Not perfectly, but as a reasonable first-order approximation. I understand that 25 years ago it might have been reasonable to argue that pixels aren't squares. But today... aren't they, at least as a first-order approximation? (With some further adjustments to avoid antialiasing artifacts, desired sharpness, and so forth.) The idea that pixels are primarily point samples seems far more misleading -- as if they were analagous to audio samples which are point samples as a first-order approximation, but pixels are nothing like audio samples.

3dee 6y ago
They are exactly like audio point samples. Pixels are always interpolated, just like audio. The fact that 1080 pixels exactly fit 1080 screen pixels don't give pixels a shape. And by the way, most modern display pixels are not squares. They come in all kinds of shapes. Triangles for example.
skavi 6y ago
The AMOLED displays in most higher end phones definitely do not have square pixels.
- ksec 6y ago
  I think you mean Pentile Sub pixel. The Pixel itself are still square.
  - numpad0 6y ago
    Pixel itself are like ////// and not square
6y ago

acomjean 6y ago

One of the weird experiences I had in college was working for the paper in the 90s. We has desktop publishing but the photos for the paper were taken out back to a machine with a screen copied them into solid black dots of various sizes. They were waxed onto printed newspaper pages and wisked off to the printer. I often wondered how you would reproduce it digitally but apparently I was thinking about it wrong. Halftone is the term https://en.m.wikipedia.org/wiki/Halftone https://en.m.wikipedia.org/wiki/Halftone