9 ms·

Sub-pixel rendering isn't really worth it on high DPI displays like this. It also doesn't work that well with iOS's CoreAnimation compositing model. Blending

by panic 11y ago

Sub-pixel rendering isn't really worth it on high DPI displays like this. It also doesn't work that well with iOS's CoreAnimation compositing model. Blending sub-pixels properly across transparent layers in particular is difficult.

tgb 11y ago
Does the apple watch downscale like their phones? Can apple implement subpixel downscaling? It seems like an easy win if already downscaling abbreviations if you can do it in hardware.
- appletree 11y ago
  Hardware gets a flat image. It can't differentiate between foreground text and background. It has to be done by the compositing layer.
  - tgb 11y ago
    I'm not convinced that is necessary. Here's my first thought. If I'm given a higher resolution image and am to downscale, knowing it will be displayed on a particular screen, then I would sample the blue pixel not from the "center of the pixel" but from the position of the blue dot in the screen. Similarly for red and green pixels. Couldn't an approach like that give subpixel precision?
    - eridius 11y ago
      If you're guaranteed that the image is displayed properly aligned to pixel boundaries, then doing that might do something, but it's probably not worth it. Which it probably will be, but it's certainly not guaranteed.
TheLoneWolfling 11y ago
> Sub-pixel rendering isn't really worth it on high DPI displays like this. [Citation Needed]
- joshuapants 11y ago
  The whole point of sub pixel rendering is to make text look like it's higher resolution. Once you get to a sufficiently high DPI there's no benefit to it.
  - TheLoneWolfling 11y ago
    Yes. However, the question is "are apple displays "sufficiently high DPI"". They are higher DPI than most other displays - but that is not the same thing.
    - simonh 11y ago
      The whole point of Retina displays is that the pixels are below the level of the average eye's ability to discern them individually. That's where the Retina monicker comes from. Asking for a citation for a well known issue, that's been widely reported for years, isn't going to win you many friends.
      - TheLoneWolfling 11y ago
        You're forgetting movement. See my other comment: https://news.ycombinator.com/item?id=9849223 https://news.ycombinator.com/item?id=9849223
    - userbinator 11y ago
      When the (whole) pixels are already small enough to the extent of being almost invisible to the naked eye, there's no point in trying to squeeze more resolution out by using individual subpixels.
      - TheLoneWolfling 11y ago
        You're forgetting movement. See my other comment: https://news.ycombinator.com/item?id=9849223 https://news.ycombinator.com/item?id=9849223
    - 11y ago
pilsetnieks 11y ago
The Apple Watch has 290/302 dpi which barely qualifies as high DPI. 290 is just below their own stated Retina threshold. Anyway, I hope they'll have a better screen for 2nd or 3rd gen watch. Edit: The numbers are wrong, it's 326 dpi for both because I couldn't be bothered to check the math of the retina display wikipedia article.
- arrrg 11y ago
  Both screens have equal pixel densities and have 326 ppi (the larger screen has consequently more pixels). Where do you get your 290/302 ppi from? That’s just wrong. The display of the 38 mm watch (38 mm refers to the height of the whole watch body, including bezel – it’s ill-fitted for calculating pixel density) is 21.22 mm wide (0.8354 inches) and has 272 horizontal pixels. That’s 325.6 ppi. The display of the 42 mm watch is 24.34 mm wide (0.9583 inches) and has 312 horizontal pixels. That’s also 325.6 ppi. That’s the same pixel density as the iPhone (excluding the 6+ with a higher pixel density and older non-retina iPhones). Now you can argue about whether typical viewing distances for watches are closer or farther than for phones (whether or not a screen is “Retina” is always a function of the typical viewing distance and the pixel density, never pixel density alone and there is no single device independent pixel density that is “Retina”), though I actually think on balance they are probably slightly farther or the same.
  - pilsetnieks 11y ago
    You're correct, someone screwed up in Wikipedia (the Retina display page) and I didn't bother to check the math.

by panic 11y ago

tgb 11y ago

Does the apple watch downscale like their phones? Can apple implement subpixel downscaling? It seems like an easy win if already downscaling abbreviations if you can do it in hardware.

appletree 11y ago
Hardware gets a flat image. It can't differentiate between foreground text and background. It has to be done by the compositing layer.
- tgb 11y ago
  I'm not convinced that is necessary. Here's my first thought. If I'm given a higher resolution image and am to downscale, knowing it will be displayed on a particular screen, then I would sample the blue pixel not from the "center of the pixel" but from the position of the blue dot in the screen. Similarly for red and green pixels. Couldn't an approach like that give subpixel precision?
  - eridius 11y ago
    If you're guaranteed that the image is displayed properly aligned to pixel boundaries, then doing that might do something, but it's probably not worth it. Which it probably will be, but it's certainly not guaranteed.

TheLoneWolfling 11y ago

> Sub-pixel rendering isn't really worth it on high DPI displays like this. [Citation Needed]

joshuapants 11y ago
The whole point of sub pixel rendering is to make text look like it's higher resolution. Once you get to a sufficiently high DPI there's no benefit to it.
- TheLoneWolfling 11y ago
  Yes. However, the question is "are apple displays "sufficiently high DPI"". They are higher DPI than most other displays - but that is not the same thing.
  - simonh 11y ago
    The whole point of Retina displays is that the pixels are below the level of the average eye's ability to discern them individually. That's where the Retina monicker comes from. Asking for a citation for a well known issue, that's been widely reported for years, isn't going to win you many friends.
    - TheLoneWolfling 11y ago
      You're forgetting movement. See my other comment: https://news.ycombinator.com/item?id=9849223 https://news.ycombinator.com/item?id=9849223
  - userbinator 11y ago
    When the (whole) pixels are already small enough to the extent of being almost invisible to the naked eye, there's no point in trying to squeeze more resolution out by using individual subpixels.
    - TheLoneWolfling 11y ago
      You're forgetting movement. See my other comment: https://news.ycombinator.com/item?id=9849223 https://news.ycombinator.com/item?id=9849223
  - 11y ago

pilsetnieks 11y ago

The Apple Watch has 290/302 dpi which barely qualifies as high DPI. 290 is just below their own stated Retina threshold. Anyway, I hope they'll have a better screen for 2nd or 3rd gen watch. Edit: The numbers are wrong, it's 326 dpi for both because I couldn't be bothered to check the math of the retina display wikipedia article.

arrrg 11y ago
Both screens have equal pixel densities and have 326 ppi (the larger screen has consequently more pixels). Where do you get your 290/302 ppi from? That’s just wrong. The display of the 38 mm watch (38 mm refers to the height of the whole watch body, including bezel – it’s ill-fitted for calculating pixel density) is 21.22 mm wide (0.8354 inches) and has 272 horizontal pixels. That’s 325.6 ppi. The display of the 42 mm watch is 24.34 mm wide (0.9583 inches) and has 312 horizontal pixels. That’s also 325.6 ppi. That’s the same pixel density as the iPhone (excluding the 6+ with a higher pixel density and older non-retina iPhones). Now you can argue about whether typical viewing distances for watches are closer or farther than for phones (whether or not a screen is “Retina” is always a function of the typical viewing distance and the pixel density, never pixel density alone and there is no single device independent pixel density that is “Retina”), though I actually think on balance they are probably slightly farther or the same.
- pilsetnieks 11y ago
  You're correct, someone screwed up in Wikipedia (the Retina display page) and I didn't bother to check the math.