Re: Pixel, Points and Spatial Measures

Question? Why does Gmail print paragraphs is funny cupets? My letters
always look strange.

Wayne

On Fri, Jan 13, 2017 at 8:09 AM, Wayne Dick <wayneedick@gmail.com> wrote:
> If this problem was easy, it would have been solved. There is a lot we
> can do to bridge the gap between web size and spacial size. We are
> making guidelines and giving techniques.
>
> The mean critical print size for text on  paper and computer has been
> calculated. Web developers will want to use this because people won't
> read there site if they deviate to much from that value. That is a
> well established fact. It is generally about .347cm on paper and
> .416cm for computer screens. We recommend in techniques that
> developers use the pixel equivalent these for their base  font... And
> we give them tables to calculate these values.
>
> I can look up common platforms and compute the pixel size needed to
> achieve critical print size. We then put it in a bunch of tables as
> guidelines for platform types with guidance on how to use them. Once
> we have spread sheets with the proper formulas, mostly trigonometric,
> we can update our tables to match common platforms in use with
> technique updates. Will it be perfect, no. Will it be better than what
> we do. Yes a lot.
>
> From this foundation, percentage has meaning. Without it, percentage
> is meaningless as an effective accommodation.
>
> I really think we should avoid the word point in our standard.
> Developers are not the only professional users of WCAG.  Disability
> lawyers don't think of point as being .75 pixels, and imprecise
> measurements will not help medical arguments in court.
>
> Patrick, we are introducing new accessibility methods. LVTF was very
> careful to identify bedrock needs. They are no more disruptive than
> the original 2.0 methods were, but they will require developers to
> think about other factors. Some of them will be difficult just like
> programmatic determinism was difficult.
>
> This problem really is solvable.
>
> Wayne
>
>
>
> On Fri, Jan 13, 2017 at 6:59 AM, Wayne Dick <wayneedick@gmail.com> wrote:
>> On Fri, Jan 13, 2017 at 6:59 AM, Wayne Dick <wayneedick@gmail.com> wrote:
>>> On Fri, Jan 13, 2017 at 1:52 AM, Alastair Campbell
>>> <acampbell@nomensa.com> wrote:
>>>> Wayne wrote:
>>>>> In web jargon 12pt = 16px, a flexible measure... We will ultimately talk to web developers in pixels because pixel is the unit of web measurement. I propose omitting the use of point size as a measure in our discussions and speak only in pixels for screens size
>>>>
>>>> That I certainly agree with, on the call last Tuesday someone made the mistake of saying points and meaning pixels, which are 25% off in terms of size. As pixels are the unit designers and devs use, they general mistake PT as meaning pixels anyway, which leads to mis-calculation of text size when doing colour contrast checks.
>>>>
>>>>
>>>>> what a person can see is determined by the angle it subtends on the retina.
>>>>
>>>> And worth noting that the CSS pixel is defined as an angle. [1]
>>>>
>>>>
>>>>> I propose that in font size issues for low vision we use spatial measures, and give conversion tables for developers. We can give our developers conversion tables in the techniques.  I can do it with centimeters and inches.
>>>>
>>>> It would be misleading to use spatial measures as the basis for the SC for web content. When a browser opens on a device, it decides what size a “CSS pixel” is.
>>>>
>>>> *Every other measurement unit is based on that CSS pixel*.
>>>>
>>>> Inches, CMs, EMs, REMs, PT, everything is based on the CSS pixel. (Percentages and VW/VH are based on viewport size, in CSS pixels.) The browser and OS convert the CSS pixels to device pixels for display (which is why stuff doesn’t get smaller on high-res screens, and occasionally you can get rounding errors).
>>>>
>>>> As I’ve said before [2,3,4] and I’ll repeat: CSS Pixels are the only relevant, semi-consistent measure for sizing web content across devices.
>>>>
>>>> As Patrick said, you could convert the other way as a rough guide, but we have to test in CSS pixels.
>>>>
>>>> -Alastair
>>>>
>>>>
>>>> 1] https://www.w3.org/TR/CSS21/syndata.html#img-pixel1
>>>> 2] https://alastairc.ac/2012/04/relative-pixels/
>>>> 3] https://alastairc.ac/2013/02/how-to-hold-your-ipad/
>>>> 4] https://alastairc.ac/2012/11/in-defence-of-pixels/
>>>>

Received on Friday, 13 January 2017 16:12:36 UTC