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Re: [css3-values] [css3-images] no units for default 'image-resolution'

From: Shelby Moore <shelby@coolpage.com>
Date: Tue, 26 Oct 2010 16:30:55 -0400
Message-ID: <7ee2d1e11df1b3e86270858b04d6cc57.squirrel@sm.webmail.pair.com>
To: shelby@coolpage.com
Cc: "Tab Atkins Jr." <jackalmage@gmail.com>, www-style@w3.org
>>> On Tue, Oct 26, 2010 at 9:50 AM, Shelby Moore <shelby@coolpage.com>
>>> wrote:
>>>> The 'px' is defined to respect relative ocular psychophysics:
>>>>
>>>> http://www.w3.org/TR/CSS21/syndata.html#numbers
>>>> http://www.w3.org/TR/css3-values/#relative0
>>>>
>>>> The 'image-resolution' is by default 1 device pixel ('dppx'):
>>>>
>>>> http://dev.w3.org/csswg/css3-images/#image-resolution
>>>> http://www.w3.org/TR/css3-images/#resolution-units
>>>>
>>>> But there exists no image pixel unit, i.e. 'px' is not equivalent to
>>>> an
>>>> image pixel.
>>>
>>> Yes it is: "By default, CSS assumes a resolution of one image pixel
>>> per CSS ?px? unit; however, the ?image-resolution? property allows
>>> using some other resolution."
>>>
>>> 1dppx means "1 image pixel = 1 CSS px".
>>
>> My mistake.  For some reason in my haste, I thought dppx meant number of
>> device pixels, but of course it says "dots per ‘px’ unit".
>>
>> Juggling too many balls today I guess. Sorry.
>
> I think it is the 'dppx', the 'dp' registers in my mind as an abbreviation
> for 'device per' or 'device pixels'. Now I see it means 'dots per', but
> I've never seen 'image pixels' referred to as dots. Is there any
> precedent?
>
> [snip]

DPI is an ambiguous term and is discouraged:

http://en.wikipedia.org/wiki/Dots_per_inch

It is advised instead to use PPI.

Thus I suggest you change 'dppx' to 'pppx'.

Also 'image resolution' is ambiguous:

http://en.wikipedia.org/wiki/Image_resolution#Pixel_resolution

I think you need to change this to 'image-spatial-resolution'.
Received on Tuesday, 26 October 2010 20:31:23 GMT

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