Such far-reaching innovation [LWN.net]

Such far-reaching innovation

Posted Aug 8, 2013 20:11 UTC (Thu) by jimparis (guest, #38647)
In reply to: Such far-reaching innovation by ncm
Parent article: High resolution displays and GNOME

> "Abstract pixel" reads, to me, an awful lot like "point", as in "11-point Garamond type". Haven't we been down this road a few times already?

Yeah, but I think people are only recently starting to realize that sizing things in points doesn't make much sense either, now that we have cell phones, desktops, and TVs all running the same code. Something like CSS3's px (which is really just 1px = 0.0213 arcseconds) is much better.

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Such far-reaching innovation

Posted Aug 9, 2013 4:28 UTC (Fri) by Ben_P (guest, #74247) [Link] (1 responses)

Having 1px defined in terms of arcseconds sounded fantastic; but http://www.w3.org/TR/2013/CR-css3-values-20130730/#absolu... ?

Such far-reaching innovation

Posted Aug 9, 2013 15:23 UTC (Fri) by jimparis (guest, #38647) [Link]

> Having 1px defined in terms of arcseconds sounded fantastic; but http://www.w3.org/TR/2013/CR-css3-values-20130730/#absolu... ?

That's the page I was reading (except I messed up the units). I think it's saying that you have the option of scaling 1px so that it matches a particular angular size, when it makes sense:

"For a CSS device, these dimensions are either anchored (i) by relating the physical units to their physical measurements, or (ii) by relating the pixel unit to the reference pixel ... For such devices it is recommended that the pixel unit refer to the whole number of device pixels that best approximates the reference pixel."

"The reference pixel is the visual angle of one pixel on a device with a pixel density of 96dpi and a distance from the reader of an arm's length. For a nominal arm's length of 28 inches, the visual angle is therefore about 0.0213 degrees."

Angular inspiration

Posted Aug 9, 2013 5:38 UTC (Fri) by ncm (guest, #165) [Link] (1 responses)

I acknowledge that an angular measure is technically better than an absolute linear measure. But everybody knows what 10-point type looks like in a book held in your hands, and the ratio of (variable) height to (standard) distance is an angular measure -- indeed, radians, if you were to use the same units. And, keeping things integral is a good idea, but not exactly earth-shaking.

But I find it hard to believe 0.0213 arcseconds for any visible pixel-like object. 10-point type at 18 inches subtends 1.6K arcseconds = 24 arcminutes, or 7.7K μradians. Probably you mean 0.0213 degrees at 28 inches (which is pretty far away). So, a pretty good size for a point is 770 μradians.

Angular inspiration

Posted Aug 9, 2013 15:25 UTC (Fri) by jimparis (guest, #38647) [Link]

I messed up the units; you're correct. CSS says 0.0213 degrees for the "reference pixel".