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The article states "Whereas subpixel rendering sacrifices color to gain resolution, the Apple II sacrificed resolution to gain color." Steve Wozniak, the designer of the Apple II, would disagree with this claim. See [1] where he is quoted as saying: "more than twenty years ago, Apple II graphics programmers were using this 'sub-pixel' technology to effectively increase the horizontal resolution of their Apple II displays." (emphasis added). Drew3D 18:14, 1 March 2006 (UTC)
I've rewritten the section to explain the Apple II graphics mode in hopefully enough detail (perhaps too much!) to explain how it both is and is not subpixel rendering depending on how you look at it. Gibson is right if you think of the screen as having 140 color pixels horizontally, which is not unreasonable if you're doing color software, but when programming it you wouldn't plot purple and green pixels, you'd just plot white pixels (which would show up purple or green or white, depending on what was next to them and whether they were at even or odd coordinates). The Apple II did have a true subpixel rendering feature (a half-pixel shift when painting with certain colors) that was exploited by some software, but it bears no relation to LCD subpixel rendering as described in this article. Jerry Kindall 16:23, 2 March 2006 (UTC)
The Apple II section is incorrect, no matter what Woz said. The Apple II is not capable of subpixel rendering because every pixel is the same size - no matter what color. If purple or green pixels on the screen were half the size of white pixels, then you'd have subpixel rendering. If you disagree, if you believe that the Apple II is capable of subpixel rendering, then please show me a screenshot of a color Apple II display on which a colored pixel is physically smaller than a white pixel. Otherwise, the "Subpixel Rendering and the Apple II" section needs to be edited down to remove the irrelevant discussion of why 1-bit hi-res bitmaps suddenly take on fringes of color when they're interpreted as color bitmaps. - Brian Kendig 18:10, 19 March 2006 (UTC)
...it doesn't actually plot a fractional pixel but a full pixel shifted half a pixel's width to the right.
Apple II really has the subpixel rendering. We agree that the color pixel effectively consumes 2 horizontal pixels in the monocrome unit. In the mono unit we have 280 horizontal points. The point is that, we can emulate 280 * 2 horizontal pixels. In this sense, the statement above by Woz and the claim by Gibson is totally irrelevant. (They mean 280 monocrome pixels are subpixel rendering of 140 color pixels.)
To see this, let us concentrate on the monocrome mode, i.e. using mono CRT monitor. Apple II's normal HGR (High-Res graphic) mode has 280 horizontal points. Let compare two commands.
versus
The first one looks like a vertical line, but the second looks like a tilted line. In effect, we have only 1/2 unit shift, even in the mono unit!. If you draw a line in this way, we can make use of 280*2 = 560 horizontal points.
This technique is described in, for example Beagle Bros' tip #5. See [2], page 19. This subpixel method is used in rounding some fonts (of course meaningful in the mono monitors) in various games. Ugha ( talk) 02:21, 12 February 2008 (UTC)
Actually, I found in the main text that the following was already contained:
This is what I mean, and really realize fractional pixel positions. Anyway the last statement depends. In the sense we cannot completely control all the subpixels, this was not successful as LCD subpix rendering, but at least this was the primitive forms of subpix rendering. Ugha ( talk) 15:08, 13 February 2008 (UTC)
Could someone add some samples at 1:1 resolution for common LCD colour orders? It's be nice to be able to compare different techniques' output. -- njh 08:47, 31 May 2006 (UTC)
so crt's don't benefit from sub-pixel rendering? What is the term then for rendering sub-pixels to more accurately determine a pixel's color?
Perhaps, not the best place to ask, but does anyone know why subpixel rendering is not used for CRT? The geometry of the screen is known perfectly well and pixels are relatively distinctive
and keep their position respective of each other. So it should be possible to do the same as cleartype does, but apparently this isn't done. Why?
I just realized that you misinterpretted me with:
I didn't mean sub-pixels red, green, blue, I meant sub-pixels as meaning greater internal resolution. Antialiasing, which the topic above meandered off to, is specifically about JAGGINESS, e.g. within a diagonal line. But I don't mean compensating for jagginess. I mean, if you render ---------------------------->
entirely confined to a pixel, then if your internal resolution matches the physical resolution, you might well end up simply deciding on a very different color than if you decide to render it internally at a full 1600 x 1200 and then average all those pixels. For example, the thumbnail I inserted above has a DIFFERENT AVERAGE PIXEL VALUE than the full picture, which is at 1024x768. However, because the picture is a mathematical abstraction, we can render it even more deeply. (Approaching closer and closer to the full fractal). For example, I am certain that the full 1024x768 picture linked above was not merely rendered by solving the equation at each point at a center of a pixel. (ie the equation was not only solved 786,432 times). Rather, I bet the software that rendered that picture rendered probably a dozen points for each pixel, maybe more, to better approximate the final fractal. However, and here's the rub, some black-and-white fractals end up completely black if you render them to infinity, and others disappear (for example the fractal defined thus: a line such that the middle third is removed and the operation is repeated on the left and the right third, ad infinitum -- if you render this "fully" you get no line to see at all.) So I'm most certainly not talking about rendering green, red, blue pixels. I'm talking about rendering pixels that are at a greater granularity to your target, which I think is called oversampling. Of course, this applies especially to cases where a mathematical abstraction certainly lets us get exact sub-values. You can't apply it to a photograph at a given resolution to get more accurate pixels.
A Special Misunderstanding
I don't think this is true for a few different reasons. First of all, when we're talking about full colors, the kind of rendering I'm thinking of is appropriate at 16 or 32 bits of colorspace. And secondly, the reason it still helps to have greater internal resolution is because when your view shifts slightly over time (as with a 3D game) the granulity of your final pixels reveals, over motion, finer detail. It's the same as a fence you can't see through because it leaves only little slivers open -- the slivers are like the final pixels -- but behind that, there's a whole lot more resolution you're just being shown a slice of, and as you move around, you can make out everything behind that fence, just from that one sliver. Or try this: make a pinhole in a piece of paper and look at it from far away that you can only make out a tiny bit of detail behind it (so, only a few pixel's worth of resolution). Now jitter it around in time, and you can see that because of how the slice changes you get a lot of the "internal" resolution hidden behind those few pixels. Or notice how a window screen (graininess) disappears if you move your head around quickly and you see the full picture behind it.
Sorry for the rambling. Is "oversampling" the only term for the things I've described? - 11:03, 10 June 2006, 87.97.10.68
Re: the Mandelbrot set pictures (more of which at User:Evercat), I wrote the program and yes, it did indeed use more than 1024x768 points (actually a lot more, though I don't recall the precise number, but it was probably at least 4 and maybe 9 or 16 subsamples per actual pixel), with the final colour for a pixel the average of the subpixels.... Evercat 21:29, 12 July 2006 (UTC)
Just wondering if it wouldn't make for sense to resize the first picture. At full size it shows pixel images blown up by a factor of 6. I think it would make more sense to reduce the thumbnail image also by a factor of 6 to render the blown up pixels as 1:1 and prevent strange artifacts being introduced. —The preceding unsigned comment was added by 82.10.133.130 ( talk • contribs) 09:33, 17 August 2006 (UTC)
I have just decided that ClearType is one of my favorite things about Windows, and I am wondering to what extent it is used and available in Linux.
All the examples assume that LCD sub-pixels are rectangular, making a square pixel. But this isn't always the case - I've just noticed that my two seemingly identical monitors are different - one has the standard pattern, the other has chevron shaped subpixels (a bit like this: >>>) I don't think there's much effect on sub-pixel rendering as they're both based on a square, but it does explain why one always looks slightly more focused than the other. Elliot100 13:34, 14 September 2006 (UTC)
The chevrons are to increase the viewing cone of the LCD, each half of the chevron has a slightly different best angle, the two average together to keep the same average behavior over the wider span of view. The angles can affect the percieved sharpness of the edges of the fonts if the base resolution is low. If the base resolution is high, it wouldn't make much difference.
66.7.227.219 02:42, 29 September 2007 (UTC) Sunbear
Interesting. Can't see any difference in viewing cone but I think the sharpness is perceivable (they are dual so I can drag a test image across the divide). Odd though that they are otherwise identical; same model. Elliot100 13:34, 14 September 2006 (UTC) —Preceding unsigned comment added by 141.228.106.136 ( talk)
There are a few ways in which subpixel rendering can be used on existing graphic formats:
But are there any graphic formats out there that are specially designed to support subpixel rendering? This might improve the rendering quality of certain kinds of images, if the same graphic file can be rendered in terms of the subpixel layout of each device it is rendered on (or in the lack of a discernable subpixel layout, plain pixel rendering). (For that matter, does JPEG already make this possible to any real extent?) -- Smjg 12:40, 10 April 2007 (UTC)
Would this technique not work on at least some CRT displays, for example an aperture grille? OS X's font smoothing seemed to work fine on my old trinitron. — Michael Z. 2007-06-13 23:14 Z
I don't think so. That doesn't sound quite right.
217.229.210.187 18:52, 4 August 2007 (UTC)
Actually, yes they did. Two engineers appled for the patent in 1988: Benzschawel, T., Howard, W., “Method of and apparatus for displaying a multicolor image” U.S. Patent #5,341,153 (filed June 13, 1988, issued Aug. 23, 1994, expired 3 Nov. 1998)
66.7.227.219 02:30, 29 September 2007 (UTC)Sunbear
An ideal LCD would have a very small "blurring" optical filter on top of each pixel, such that the pixel looks uniformly white, rather than having 3 vertical coloured stripes. This does actually seem to be the case: I observed the LCD on my laptop (Thinkpad T60p) through a strong zoom lens (300mm macro lens, with x2 converter, OM2 camera, very small depth-of-field), and saw the following:
So, it seems that this LCD, at least, has a small optical blurring filter applied in front of it, to improve the quality. [That would also be why the human eye can't see the coloured sub-pixels, even though a 100um wide feature should be visible to those with good vision]
In such an LCD, sub-pixel rendering makes the image much worse; the effect is colour-fringing around each letter.
Can anyone confirm or explain this? RichardNeill 02:35, 14 September 2007 (UTC)
Um, you are seeing the effects of being out of focus. If there was a blurring filter on the lcd, then you wouldn't be able to focus through it, just like you can't focus through a frosted glass window. And if there was a blurring filter, sub-pixel rendering still wouldn't have a significant detrimental effect. The colour fringing should be invisible to the eye under most conditions. 122.107.20.56 ( talk) 10:51, 1 May 2008 (UTC)
You are looking at the effect of the different layers of the LCD. There is an anti-glare filter on the surface. It does have the beneficial effect of being a reconstruction filter. It is not there to be so though... and it isn't to blur the color subpixels together, your eye does that just fine. This would not affect the subpixel rendering performance unless the filter was extremely blurry. I suspect that you have a non-standard order to the colors and have not used the optimizer to set-up the algorithm accordingly.
66.7.227.219 02:38, 29 September 2007 (UTC) Sunbear
I have created and uploaded two images which I originally drew to try to figure out a better way to do subpixel antialiasing on my LCD screen. Do these images seem like something that can be used for this page? The first image is on the right, and was drawn explicitly to demonstrate LCD subpixel positioning, and it compares normal greyscale antialiasing with raw subpixel antialiasing (the ugly kind :-) ) and a sort of "filtered" subpixel antialiasing, along with some color scales to let the user see the way the filter works, how the subpixels are positioned, and examples of Times-roman letter "A" in non-antialiased, greyscale-antialiased, raw-subpixel-antialiased, and filtered-subpixel-antialiased forms.
I kinda screwed up the "filter" as I drew this image, but it is based very loosely on something I read elsewhere on the web. If done right, each subpixel to be drawn gets its brightness cut to 50% of whatever it was originally, while the two neighboring subpixels are then set to 25% of the original value, and added to whatever else needs to be plotted and/or is already on the screen. For example, A single "white" dot 1/3 pixel wide plotted on a black background where a physical red subpixel is, would result in a dark blue (0,0,0.25) pixel to the left of a brownish-orange (0.5,0.25,0) pixel. The result is kind of grayish, but you can't exactly draw a 1/3 pixel wide white line. Make the line two or three subpixels wide and it turns mostly white. Either way, it has the effect of antialiasing a drawn image and seems to do well at getting rid of subpixel antialiasing color fringing once and for all.
This second image is a scaled-up version of the first, filtered to create a simulation of what an LCD monitor would do with the original image. Comments are appreciated - I would love to see someone implement this method in Linux/Freetype/Cairo etc.
Vanessaezekowitz ( talk) 02:03, 30 June 2008 (UTC)
ClearType was not an implementation of the IBM invention, which nobody knew about until it was dug up after ClearType came out. When did Apple's version come out? After Microsoft? The original invention by a couple programmers in e-Books was clever but somewhat ad hoc, similar to what Gibson came up with, but with some attempt to filter. Then the problem was analyzed in MS Research, where it was demonstrated that in fact the method could be used on arbitrary image rendering (MS only uses it for fonts). The problem was then turned over to John Platt, an expert on signal processing and filter design, who created a much improved version that uses a specially designed FIR filter. 24.16.92.48 ( talk) 14:11, 15 July 2008 (UTC) DonPMitchell ( talk) 14:12, 15 July 2008 (UTC)
As an interesting historical note, Microsoft announced ClearType just 12 days after the IBM patent on subpixel rendering was allowed to lapse into the public domain for failure to pay the mataintance fees. DisplayGeek ( talk) 19:40, 30 March 2010 (UTC)
Also of important historical note, Candice Brown Elliott, the founder of Clairvoyante and Nouvoyance, the inventor of the PenTile Matrix Family of layouts, first experimented with subpixel rendering on a red/green stripe electroluminescent panel in 1992 when she was an R&D scientist at Planar Systems in 1992. She invented the first of the PenTile layouts in 1993 and continued to work on them independently until she founded in Clairvoyante in 2000. DisplayGeek ( talk) 19:44, 30 March 2010 (UTC)
Note that FreeType with the subpixel rendering functionality shown in these examples cannot be distributed in the United States due to the patents mentioned above.
It can now. The patents expired in May 2010.
The article barely mentions what can be done about "color fringes". With text rendering, this is an absolutely crucial part - the subpixel rendering process before that is downright trivial. In practice, current font rendering systems apply a smoothing filter in subpixel direction to reduce fringes and apply gamma correction to reduce the "smudgy" look. I think this should be discussed either in this article or in Font rasterization.
The article's lede says that subpixel rendering is for LCD and OLED devices—among other devices with fixed subpixels, plasma displays have them (at least according to the Wikipedia article). Someone posted a question on Talk:ClearType about printers. Anyone know if subpixel rendering has been used on any hard output devices? Bongo matic 05:35, 4 December 2011 (UTC)
I added colour as a visual aid to better convey the subtle matrix differences (feedback welcome per WP:COLOUR) - note white on black background was too invasive, and yellow and cyan are better as background due to contrast. I let this bold change bake a bit on PenTile matrix family, RGB (rejected), Quattron already. As this is a bold edit, please discuss.
As I was there I fixed unrelated issues (overlinking, links, etc) with this edit. The pair of images in the first section "background" is confusing without further explanation i.e. why an article only about additive colours has a subtractive colour example? why "RGB" is coloured with CMY? why when adding the colours we get black? I'm guessing it is meant to demonstrate an LCD with filters?, hence all the black pixels? That is not stated, is out of context, and in my opinion only confuses at that point in the article. Anyone want to remove or fix? Widefox; talk 12:42, 24 October 2012 (UTC)
Nothing of what I know about display technology leads me to agree that an RGBW subpixel structure would have better colour reproduction than anything, let alone CMYK. (This looks more like original research--the false assumption that RGBW is "CMYK in reverse" and somehow has the same colour characteristics.) Rather, RGBW should have the exact same gamut as RGB, only with less saturation in colours with the most brightness. -- GregE ( talk) 03:50, 14 December 2012 (UTC)
I thought that subpixel rendering was available in Adobe Acrobat / Reader earlier than in Windows XP. In the Acrobat I think it was offered during initial setup by default. -- pabouk ( talk) 09:23, 8 January 2014 (UTC)
There should be some mention of its disadvantages. Maybe a whole section dedicated to it, even. Though I'm biased against ClearType and its kind. •ː• 3ICE •ː• 08:29, 29 November 2014 (UTC)
If that section comes about, one could mention that subpixel rendering makes it hard to get clean enlarged screenshots of rendered glyphs because of the color fringes. For example, one is taking screenshots of an app's UI to produce documentation, and enlarges a certain area for detail, and all the text has visible colored edges. It would be handy if, when taking a screenshot, that there was an option to exclude the subpixel rendering and switch to normal antialiasing. — Preceding unsigned comment added by 2001:569:7510:A000:1898:E49:4F20:E01D ( talk) 01:44, 4 June 2016 (UTC)
I have designed a fractal program that generates imagery with the option of oversampling with RGB or BGR subpixel rendering. It runs on any modern web browser. You can find this at www.fractalartdesign.com/fractal
The oversampling options are "none" (1x1), "good" (2x2), "detailed" (4x4), and "fine" (8x8) under the "Quality" menu. Exceeding 8x8 oversampling provides no further gain in clarity. When subpixel-rendering is engaged under the "Render" menu, the oversampling adjusts to 6x4 and 9x8 to distribute it over the three primaries, effectively tripling the horizontal resolution of the fractal. It is not engaged under the "none" or the "good" options, as applying subpixels in 3x1 or 3x2 oversampling causes marked color distortion.
It does make a difference in the detail of the rendered fractal on an LCD display. Subpixel-rendered images seem sharper. When rendering for print or publication, this option must be turned off to avoid the fringing artifacts.
I attempted to upload samples for consideration in the article, but Wikipedia rejected the uploads as "unknown" in appropriateness.
Gsearle5 ( talk) 20:21, 23 September 2016 (UTC)
I'm not sure if this quite fits in with this topic, but it is very interesting in itself. I found references to an electronic slide viewer called VideoShow and its accompanying software, PictureIt, by a company called General Parametrics. One of the selling points was the control over the horizontal positioning of display elements by apparently addressing the individual phosphors on a CRT display, effectively increasing the horizontal resolution. Here are the news articles and reviews:
-- PaulBoddie ( talk) 23:06, 15 August 2022 (UTC)
Another article:
-- PaulBoddie ( talk) 21:44, 4 October 2022 (UTC)
It's simply not true. Videogame artists have been taking advantage of subpixel rendering for decades. This is why SNES and PS1 era art looks so much better at 1:1 native resolution than blow up as raw bitmaps of square pixels. It's why people prefer low resolution displays like CRTs for those games. In fact, for years I was fascinated by Windows XPs "ClearType" on my CRT monitors. This was technology designed for CRT long before LCD monitors became commonplace. The fact that it also works on LCD, and everyone now uses LCD, doesn't imply it's for LCD only. The article would be more accurate if it simply said LCD/CRT without vaguely claiming there's a difference in their subpixel rendering abilities. There isn't. Habanero-tan ( talk) 00:59, 26 September 2022 (UTC)
References
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The article states "Whereas subpixel rendering sacrifices color to gain resolution, the Apple II sacrificed resolution to gain color." Steve Wozniak, the designer of the Apple II, would disagree with this claim. See [1] where he is quoted as saying: "more than twenty years ago, Apple II graphics programmers were using this 'sub-pixel' technology to effectively increase the horizontal resolution of their Apple II displays." (emphasis added). Drew3D 18:14, 1 March 2006 (UTC)
I've rewritten the section to explain the Apple II graphics mode in hopefully enough detail (perhaps too much!) to explain how it both is and is not subpixel rendering depending on how you look at it. Gibson is right if you think of the screen as having 140 color pixels horizontally, which is not unreasonable if you're doing color software, but when programming it you wouldn't plot purple and green pixels, you'd just plot white pixels (which would show up purple or green or white, depending on what was next to them and whether they were at even or odd coordinates). The Apple II did have a true subpixel rendering feature (a half-pixel shift when painting with certain colors) that was exploited by some software, but it bears no relation to LCD subpixel rendering as described in this article. Jerry Kindall 16:23, 2 March 2006 (UTC)
The Apple II section is incorrect, no matter what Woz said. The Apple II is not capable of subpixel rendering because every pixel is the same size - no matter what color. If purple or green pixels on the screen were half the size of white pixels, then you'd have subpixel rendering. If you disagree, if you believe that the Apple II is capable of subpixel rendering, then please show me a screenshot of a color Apple II display on which a colored pixel is physically smaller than a white pixel. Otherwise, the "Subpixel Rendering and the Apple II" section needs to be edited down to remove the irrelevant discussion of why 1-bit hi-res bitmaps suddenly take on fringes of color when they're interpreted as color bitmaps. - Brian Kendig 18:10, 19 March 2006 (UTC)
...it doesn't actually plot a fractional pixel but a full pixel shifted half a pixel's width to the right.
Apple II really has the subpixel rendering. We agree that the color pixel effectively consumes 2 horizontal pixels in the monocrome unit. In the mono unit we have 280 horizontal points. The point is that, we can emulate 280 * 2 horizontal pixels. In this sense, the statement above by Woz and the claim by Gibson is totally irrelevant. (They mean 280 monocrome pixels are subpixel rendering of 140 color pixels.)
To see this, let us concentrate on the monocrome mode, i.e. using mono CRT monitor. Apple II's normal HGR (High-Res graphic) mode has 280 horizontal points. Let compare two commands.
versus
The first one looks like a vertical line, but the second looks like a tilted line. In effect, we have only 1/2 unit shift, even in the mono unit!. If you draw a line in this way, we can make use of 280*2 = 560 horizontal points.
This technique is described in, for example Beagle Bros' tip #5. See [2], page 19. This subpixel method is used in rounding some fonts (of course meaningful in the mono monitors) in various games. Ugha ( talk) 02:21, 12 February 2008 (UTC)
Actually, I found in the main text that the following was already contained:
This is what I mean, and really realize fractional pixel positions. Anyway the last statement depends. In the sense we cannot completely control all the subpixels, this was not successful as LCD subpix rendering, but at least this was the primitive forms of subpix rendering. Ugha ( talk) 15:08, 13 February 2008 (UTC)
Could someone add some samples at 1:1 resolution for common LCD colour orders? It's be nice to be able to compare different techniques' output. -- njh 08:47, 31 May 2006 (UTC)
so crt's don't benefit from sub-pixel rendering? What is the term then for rendering sub-pixels to more accurately determine a pixel's color?
Perhaps, not the best place to ask, but does anyone know why subpixel rendering is not used for CRT? The geometry of the screen is known perfectly well and pixels are relatively distinctive
and keep their position respective of each other. So it should be possible to do the same as cleartype does, but apparently this isn't done. Why?
I just realized that you misinterpretted me with:
I didn't mean sub-pixels red, green, blue, I meant sub-pixels as meaning greater internal resolution. Antialiasing, which the topic above meandered off to, is specifically about JAGGINESS, e.g. within a diagonal line. But I don't mean compensating for jagginess. I mean, if you render ---------------------------->
entirely confined to a pixel, then if your internal resolution matches the physical resolution, you might well end up simply deciding on a very different color than if you decide to render it internally at a full 1600 x 1200 and then average all those pixels. For example, the thumbnail I inserted above has a DIFFERENT AVERAGE PIXEL VALUE than the full picture, which is at 1024x768. However, because the picture is a mathematical abstraction, we can render it even more deeply. (Approaching closer and closer to the full fractal). For example, I am certain that the full 1024x768 picture linked above was not merely rendered by solving the equation at each point at a center of a pixel. (ie the equation was not only solved 786,432 times). Rather, I bet the software that rendered that picture rendered probably a dozen points for each pixel, maybe more, to better approximate the final fractal. However, and here's the rub, some black-and-white fractals end up completely black if you render them to infinity, and others disappear (for example the fractal defined thus: a line such that the middle third is removed and the operation is repeated on the left and the right third, ad infinitum -- if you render this "fully" you get no line to see at all.) So I'm most certainly not talking about rendering green, red, blue pixels. I'm talking about rendering pixels that are at a greater granularity to your target, which I think is called oversampling. Of course, this applies especially to cases where a mathematical abstraction certainly lets us get exact sub-values. You can't apply it to a photograph at a given resolution to get more accurate pixels.
A Special Misunderstanding
I don't think this is true for a few different reasons. First of all, when we're talking about full colors, the kind of rendering I'm thinking of is appropriate at 16 or 32 bits of colorspace. And secondly, the reason it still helps to have greater internal resolution is because when your view shifts slightly over time (as with a 3D game) the granulity of your final pixels reveals, over motion, finer detail. It's the same as a fence you can't see through because it leaves only little slivers open -- the slivers are like the final pixels -- but behind that, there's a whole lot more resolution you're just being shown a slice of, and as you move around, you can make out everything behind that fence, just from that one sliver. Or try this: make a pinhole in a piece of paper and look at it from far away that you can only make out a tiny bit of detail behind it (so, only a few pixel's worth of resolution). Now jitter it around in time, and you can see that because of how the slice changes you get a lot of the "internal" resolution hidden behind those few pixels. Or notice how a window screen (graininess) disappears if you move your head around quickly and you see the full picture behind it.
Sorry for the rambling. Is "oversampling" the only term for the things I've described? - 11:03, 10 June 2006, 87.97.10.68
Re: the Mandelbrot set pictures (more of which at User:Evercat), I wrote the program and yes, it did indeed use more than 1024x768 points (actually a lot more, though I don't recall the precise number, but it was probably at least 4 and maybe 9 or 16 subsamples per actual pixel), with the final colour for a pixel the average of the subpixels.... Evercat 21:29, 12 July 2006 (UTC)
Just wondering if it wouldn't make for sense to resize the first picture. At full size it shows pixel images blown up by a factor of 6. I think it would make more sense to reduce the thumbnail image also by a factor of 6 to render the blown up pixels as 1:1 and prevent strange artifacts being introduced. —The preceding unsigned comment was added by 82.10.133.130 ( talk • contribs) 09:33, 17 August 2006 (UTC)
I have just decided that ClearType is one of my favorite things about Windows, and I am wondering to what extent it is used and available in Linux.
All the examples assume that LCD sub-pixels are rectangular, making a square pixel. But this isn't always the case - I've just noticed that my two seemingly identical monitors are different - one has the standard pattern, the other has chevron shaped subpixels (a bit like this: >>>) I don't think there's much effect on sub-pixel rendering as they're both based on a square, but it does explain why one always looks slightly more focused than the other. Elliot100 13:34, 14 September 2006 (UTC)
The chevrons are to increase the viewing cone of the LCD, each half of the chevron has a slightly different best angle, the two average together to keep the same average behavior over the wider span of view. The angles can affect the percieved sharpness of the edges of the fonts if the base resolution is low. If the base resolution is high, it wouldn't make much difference.
66.7.227.219 02:42, 29 September 2007 (UTC) Sunbear
Interesting. Can't see any difference in viewing cone but I think the sharpness is perceivable (they are dual so I can drag a test image across the divide). Odd though that they are otherwise identical; same model. Elliot100 13:34, 14 September 2006 (UTC) —Preceding unsigned comment added by 141.228.106.136 ( talk)
There are a few ways in which subpixel rendering can be used on existing graphic formats:
But are there any graphic formats out there that are specially designed to support subpixel rendering? This might improve the rendering quality of certain kinds of images, if the same graphic file can be rendered in terms of the subpixel layout of each device it is rendered on (or in the lack of a discernable subpixel layout, plain pixel rendering). (For that matter, does JPEG already make this possible to any real extent?) -- Smjg 12:40, 10 April 2007 (UTC)
Would this technique not work on at least some CRT displays, for example an aperture grille? OS X's font smoothing seemed to work fine on my old trinitron. — Michael Z. 2007-06-13 23:14 Z
I don't think so. That doesn't sound quite right.
217.229.210.187 18:52, 4 August 2007 (UTC)
Actually, yes they did. Two engineers appled for the patent in 1988: Benzschawel, T., Howard, W., “Method of and apparatus for displaying a multicolor image” U.S. Patent #5,341,153 (filed June 13, 1988, issued Aug. 23, 1994, expired 3 Nov. 1998)
66.7.227.219 02:30, 29 September 2007 (UTC)Sunbear
An ideal LCD would have a very small "blurring" optical filter on top of each pixel, such that the pixel looks uniformly white, rather than having 3 vertical coloured stripes. This does actually seem to be the case: I observed the LCD on my laptop (Thinkpad T60p) through a strong zoom lens (300mm macro lens, with x2 converter, OM2 camera, very small depth-of-field), and saw the following:
So, it seems that this LCD, at least, has a small optical blurring filter applied in front of it, to improve the quality. [That would also be why the human eye can't see the coloured sub-pixels, even though a 100um wide feature should be visible to those with good vision]
In such an LCD, sub-pixel rendering makes the image much worse; the effect is colour-fringing around each letter.
Can anyone confirm or explain this? RichardNeill 02:35, 14 September 2007 (UTC)
Um, you are seeing the effects of being out of focus. If there was a blurring filter on the lcd, then you wouldn't be able to focus through it, just like you can't focus through a frosted glass window. And if there was a blurring filter, sub-pixel rendering still wouldn't have a significant detrimental effect. The colour fringing should be invisible to the eye under most conditions. 122.107.20.56 ( talk) 10:51, 1 May 2008 (UTC)
You are looking at the effect of the different layers of the LCD. There is an anti-glare filter on the surface. It does have the beneficial effect of being a reconstruction filter. It is not there to be so though... and it isn't to blur the color subpixels together, your eye does that just fine. This would not affect the subpixel rendering performance unless the filter was extremely blurry. I suspect that you have a non-standard order to the colors and have not used the optimizer to set-up the algorithm accordingly.
66.7.227.219 02:38, 29 September 2007 (UTC) Sunbear
I have created and uploaded two images which I originally drew to try to figure out a better way to do subpixel antialiasing on my LCD screen. Do these images seem like something that can be used for this page? The first image is on the right, and was drawn explicitly to demonstrate LCD subpixel positioning, and it compares normal greyscale antialiasing with raw subpixel antialiasing (the ugly kind :-) ) and a sort of "filtered" subpixel antialiasing, along with some color scales to let the user see the way the filter works, how the subpixels are positioned, and examples of Times-roman letter "A" in non-antialiased, greyscale-antialiased, raw-subpixel-antialiased, and filtered-subpixel-antialiased forms.
I kinda screwed up the "filter" as I drew this image, but it is based very loosely on something I read elsewhere on the web. If done right, each subpixel to be drawn gets its brightness cut to 50% of whatever it was originally, while the two neighboring subpixels are then set to 25% of the original value, and added to whatever else needs to be plotted and/or is already on the screen. For example, A single "white" dot 1/3 pixel wide plotted on a black background where a physical red subpixel is, would result in a dark blue (0,0,0.25) pixel to the left of a brownish-orange (0.5,0.25,0) pixel. The result is kind of grayish, but you can't exactly draw a 1/3 pixel wide white line. Make the line two or three subpixels wide and it turns mostly white. Either way, it has the effect of antialiasing a drawn image and seems to do well at getting rid of subpixel antialiasing color fringing once and for all.
This second image is a scaled-up version of the first, filtered to create a simulation of what an LCD monitor would do with the original image. Comments are appreciated - I would love to see someone implement this method in Linux/Freetype/Cairo etc.
Vanessaezekowitz ( talk) 02:03, 30 June 2008 (UTC)
ClearType was not an implementation of the IBM invention, which nobody knew about until it was dug up after ClearType came out. When did Apple's version come out? After Microsoft? The original invention by a couple programmers in e-Books was clever but somewhat ad hoc, similar to what Gibson came up with, but with some attempt to filter. Then the problem was analyzed in MS Research, where it was demonstrated that in fact the method could be used on arbitrary image rendering (MS only uses it for fonts). The problem was then turned over to John Platt, an expert on signal processing and filter design, who created a much improved version that uses a specially designed FIR filter. 24.16.92.48 ( talk) 14:11, 15 July 2008 (UTC) DonPMitchell ( talk) 14:12, 15 July 2008 (UTC)
As an interesting historical note, Microsoft announced ClearType just 12 days after the IBM patent on subpixel rendering was allowed to lapse into the public domain for failure to pay the mataintance fees. DisplayGeek ( talk) 19:40, 30 March 2010 (UTC)
Also of important historical note, Candice Brown Elliott, the founder of Clairvoyante and Nouvoyance, the inventor of the PenTile Matrix Family of layouts, first experimented with subpixel rendering on a red/green stripe electroluminescent panel in 1992 when she was an R&D scientist at Planar Systems in 1992. She invented the first of the PenTile layouts in 1993 and continued to work on them independently until she founded in Clairvoyante in 2000. DisplayGeek ( talk) 19:44, 30 March 2010 (UTC)
Note that FreeType with the subpixel rendering functionality shown in these examples cannot be distributed in the United States due to the patents mentioned above.
It can now. The patents expired in May 2010.
The article barely mentions what can be done about "color fringes". With text rendering, this is an absolutely crucial part - the subpixel rendering process before that is downright trivial. In practice, current font rendering systems apply a smoothing filter in subpixel direction to reduce fringes and apply gamma correction to reduce the "smudgy" look. I think this should be discussed either in this article or in Font rasterization.
The article's lede says that subpixel rendering is for LCD and OLED devices—among other devices with fixed subpixels, plasma displays have them (at least according to the Wikipedia article). Someone posted a question on Talk:ClearType about printers. Anyone know if subpixel rendering has been used on any hard output devices? Bongo matic 05:35, 4 December 2011 (UTC)
I added colour as a visual aid to better convey the subtle matrix differences (feedback welcome per WP:COLOUR) - note white on black background was too invasive, and yellow and cyan are better as background due to contrast. I let this bold change bake a bit on PenTile matrix family, RGB (rejected), Quattron already. As this is a bold edit, please discuss.
As I was there I fixed unrelated issues (overlinking, links, etc) with this edit. The pair of images in the first section "background" is confusing without further explanation i.e. why an article only about additive colours has a subtractive colour example? why "RGB" is coloured with CMY? why when adding the colours we get black? I'm guessing it is meant to demonstrate an LCD with filters?, hence all the black pixels? That is not stated, is out of context, and in my opinion only confuses at that point in the article. Anyone want to remove or fix? Widefox; talk 12:42, 24 October 2012 (UTC)
Nothing of what I know about display technology leads me to agree that an RGBW subpixel structure would have better colour reproduction than anything, let alone CMYK. (This looks more like original research--the false assumption that RGBW is "CMYK in reverse" and somehow has the same colour characteristics.) Rather, RGBW should have the exact same gamut as RGB, only with less saturation in colours with the most brightness. -- GregE ( talk) 03:50, 14 December 2012 (UTC)
I thought that subpixel rendering was available in Adobe Acrobat / Reader earlier than in Windows XP. In the Acrobat I think it was offered during initial setup by default. -- pabouk ( talk) 09:23, 8 January 2014 (UTC)
There should be some mention of its disadvantages. Maybe a whole section dedicated to it, even. Though I'm biased against ClearType and its kind. •ː• 3ICE •ː• 08:29, 29 November 2014 (UTC)
If that section comes about, one could mention that subpixel rendering makes it hard to get clean enlarged screenshots of rendered glyphs because of the color fringes. For example, one is taking screenshots of an app's UI to produce documentation, and enlarges a certain area for detail, and all the text has visible colored edges. It would be handy if, when taking a screenshot, that there was an option to exclude the subpixel rendering and switch to normal antialiasing. — Preceding unsigned comment added by 2001:569:7510:A000:1898:E49:4F20:E01D ( talk) 01:44, 4 June 2016 (UTC)
I have designed a fractal program that generates imagery with the option of oversampling with RGB or BGR subpixel rendering. It runs on any modern web browser. You can find this at www.fractalartdesign.com/fractal
The oversampling options are "none" (1x1), "good" (2x2), "detailed" (4x4), and "fine" (8x8) under the "Quality" menu. Exceeding 8x8 oversampling provides no further gain in clarity. When subpixel-rendering is engaged under the "Render" menu, the oversampling adjusts to 6x4 and 9x8 to distribute it over the three primaries, effectively tripling the horizontal resolution of the fractal. It is not engaged under the "none" or the "good" options, as applying subpixels in 3x1 or 3x2 oversampling causes marked color distortion.
It does make a difference in the detail of the rendered fractal on an LCD display. Subpixel-rendered images seem sharper. When rendering for print or publication, this option must be turned off to avoid the fringing artifacts.
I attempted to upload samples for consideration in the article, but Wikipedia rejected the uploads as "unknown" in appropriateness.
Gsearle5 ( talk) 20:21, 23 September 2016 (UTC)
I'm not sure if this quite fits in with this topic, but it is very interesting in itself. I found references to an electronic slide viewer called VideoShow and its accompanying software, PictureIt, by a company called General Parametrics. One of the selling points was the control over the horizontal positioning of display elements by apparently addressing the individual phosphors on a CRT display, effectively increasing the horizontal resolution. Here are the news articles and reviews:
-- PaulBoddie ( talk) 23:06, 15 August 2022 (UTC)
Another article:
-- PaulBoddie ( talk) 21:44, 4 October 2022 (UTC)
It's simply not true. Videogame artists have been taking advantage of subpixel rendering for decades. This is why SNES and PS1 era art looks so much better at 1:1 native resolution than blow up as raw bitmaps of square pixels. It's why people prefer low resolution displays like CRTs for those games. In fact, for years I was fascinated by Windows XPs "ClearType" on my CRT monitors. This was technology designed for CRT long before LCD monitors became commonplace. The fact that it also works on LCD, and everyone now uses LCD, doesn't imply it's for LCD only. The article would be more accurate if it simply said LCD/CRT without vaguely claiming there's a difference in their subpixel rendering abilities. There isn't. Habanero-tan ( talk) 00:59, 26 September 2022 (UTC)
References