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Retina display supportRetina display supportPosted Jan 9, 2013 11:03 UTC (Wed) by epa (subscriber, #39769)In reply to: Retina display support by roc Parent article: Firefox 18 is now available
It means we render everything at the device resolution, so CSS 1px x 1px renders as 2x2 device pixels. It's kinda like having a default zoom.Thanks for the explanation. At work I run Firefox on Windows on a high-resolution display, and use Ctrl-+ to zoom in, which magnifies both the text and the images. Is that equivalent?
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Retina display support Posted Jan 9, 2013 12:50 UTC (Wed) by roc (subscriber, #30627) [Link]
Yes, that's pretty close.
Retina display support Posted Jan 9, 2013 17:45 UTC (Wed) by nye (guest, #51576) [Link]
Wait, so by default does that mean that images are shown at 200% zoom? Isn't that going to look terrible?
Is there any way for a site author to 'opt-out' of this? Maybe something involving a media-dependent stylesheet or something.
Retina display support Posted Jan 9, 2013 18:41 UTC (Wed) by Cyberax (✭ supporter ✭, #52523) [Link]
> Wait, so by default does that mean that images are shown at 200% zoom? Isn't that going to look terrible?
Yup. It's not that terrible in practice, but definitely not optimal.
> Is there any way for a site author to 'opt-out' of this? Maybe something involving a media-dependent stylesheet or something.
Retina display support Posted Jan 9, 2013 21:40 UTC (Wed) by roc (subscriber, #30627) [Link]
Terrible compared to what alternatives? Showing images at half their expected size? On a Retina screen, images have to be scaled up somehow.
For non-Retina-aware apps, MacOS just scales the entire window up by a factor of 2. Being Retina-aware means for things we can scale intelligently (text, vector graphics) we do much better. For images we usually can't do much better although at least we give the author some control (choosing between nearest-neighbour and bilinear scaling via the image-rendering CSS property).
Retina display support Posted Jan 10, 2013 9:52 UTC (Thu) by epa (subscriber, #39769) [Link]
Ah, so the site author can choose nearest-neighbour scaling using a CSS property. It would be lovely if Firefox also supported hqx or other intelligent scaling methods for bitmap graphics.
Retina display support Posted Jan 10, 2013 13:08 UTC (Thu) by nye (guest, #51576) [Link]
>Terrible compared to what alternatives? Showing images at half their expected size?
No, compared to showing it at the *expected* size. If my image is 800px wide, the expected size is 800px. Stretching it to 1600px mean showing it at *double* its expected size.
>On a Retina screen, images have to be scaled up somehow.
I have here a number of displays, ranging from around 100ppi to around 250ppi. Looking at the same image on the lowest and highest density displays, it looks far better on the higher one when displayed at its native size. If that gets rescaled to make it the same *physical* size, the theoretical best case scenario is that it looks like it does on the low density display, except in practice the better display means that you can really see the deficiency of the scaling.
I recognise that there is a real problem to be solved here, where some genius has specified a text height of 12px and some background image to match (or whatever), but the solution given doesn't seem like a good one at all.
Retina display support Posted Jan 10, 2013 13:29 UTC (Thu) by nye (guest, #51576) [Link]
>I have here a number of displays, ranging from around 100ppi to around 250ppi. Looking at the same image on the lowest and highest density displays, it looks far better on the higher one when displayed at its native size. If that gets rescaled to make it the same *physical* size, the theoretical best case scenario is that it looks like it does on the low density display, except in practice the better display means that you can really see the deficiency of the scaling.
To be more specific, when looking at the same image at the same physical size and distance on both screens, the difference is that the high resolution display looks blurred - this is with whatever scaler the Android browser uses.
I *hate* blurry visuals. They're tiring to look at because my eyes keep trying harder to focus until they've had a *long* time to get used to the knowledge that they simply can't; that's something that never happens in the physical world, so it makes an unpleasant transition between looking at a screen and looking at real physical objects.
Related: the default font smoothing settings on Ubuntu (picked that only because it's the only distro I've used recently with an out-of-the-box config - maybe others are different) looks like somebody took a stick of lard and smeared it over the monitor; it disgusts me, and it's uncomfortable to read. In this area at least, high PPI displays are a clear win regardless of how images are treated.
I can see that the image-doubling behaviour would be desirable if you value large images over sharp images, but that's a position I can't even begin to empathise with in any way because my eyes find it physically unpleasant.
Retina display support Posted Jan 12, 2013 6:55 UTC (Sat) by alankila (subscriber, #47141) [Link]
Notice that pixel-doubling scaling preserves the image contrast and every other property, at the cost of not utilizing the additional resolution in any way. Things look the same despite you have double the pixels!
Interpolation filters produce errors when encountering high-frequency content of the image. These errors follow from ignored gamma correction (= scaled images tend to be too dark at high-frequency features) and modeling of image as infinitesimal points of specific color and intensity at particular points of a grid, rather than interpreting the image as an area-averaged sampling of an unknown light function. If you had a theory of the light function whose gridded area-average produced the current image, you would be able to resample such function to any resolution, and likely the results would be more natural too. In any case the upshot of the latter effect is reduction of contrast of high-frequency images. I studied the problem slightly here:
https://bel.fi/alankila/scaling/
Much more work should be done to turn this into something practical, though.
Retina display support Posted Jan 12, 2013 19:02 UTC (Sat) by jimparis (subscriber, #38647) [Link]
> If you had a theory of the light function whose gridded area-average produced the current image, you would be able to resample such function to any resolution, and likely the results would be more natural too.
There's a really simple light function that produces the current image: solid colored squares, each exactly the size of the image's pixels. Which leads exactly to the "pixel-doubling scaling" you describe. You might manage to come up with an alternate light function that also fits, but there's no way of knowing that it's any more correct.
Retina display support Posted Jan 13, 2013 0:22 UTC (Sun) by alankila (subscriber, #47141) [Link]
Acceptable, but I think some kind of gaussian blurring combined with edge enhance would be a reasonable choice for at least natural photographs. Ultimately we DO know that the image is almost certainly not composed of tiny squares of colors in the real world, perfectly aligned to fall into the camera's pixel grid, after all.
So it is my faith that we can do better than that, and not even try very hard; the trouble may be in the corner cases where it would appear that we do worse. For instance, over/undersaturation is a risk for edge enhancements that are somehow tangentially involved in algorithm like this. How would you represent color that has negative luminosity? You can't, so for some cases the algorithm would have to degrade naturally.
Retina display support Posted Jan 14, 2013 7:59 UTC (Mon) by ekj (guest, #1524) [Link]
When the image is a result of capturing the real world on a camera-sensor, then this is indeed true, and as you say, algorithms that do more funky things than pixel-doubling perform well.
But we don't know that, generally speaking. (though we can attempt to detect it) Lots of images are the result of computation, they might be output from a graphing-library, for example.
What works well for a photo of a face, doesn't always work well for output from gnuplot.
Retina display support Posted Jan 10, 2013 13:34 UTC (Thu) by mpr22 (subscriber, #60784) [Link] Rendering at 1px=1px on high-pixel-density high-pixel-count displays does not, on first inspection, look like it is likely to perform well on accessibility criteria. Converting a CSS distance of 1px into a display distance of two pixels looks rather more likely to perform well on this score. As long as those who crave tiny images can easily turn off the scaling, the default behaviour should be chosen to be kinder to those for whom tiny images are not sensible.
Retina display support Posted Jan 9, 2013 22:26 UTC (Wed) by redden0t8 (guest, #72783) [Link]
I'd go for blurry-but-visible over sharp-but-illegibly-tiny any day.
Even if all the browser did was plain pixel-doubling, you'd still end up with your image exactly as it would appear on a low-dpi monitor - the only reason it looks worse is because the rest of the screen is high res so the pixelation is more obvious.
Once you add in good anti-aliasing, IMHO even a low-dpi image scaled up on a hi-dpi display looks better than the same low-dpi image displayed natively on a low-dpi display.
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