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Re: [CSS21] 4.3.2 Lengths (reference pixel?)

From: Brad Kemper <brad.kemper@gmail.com>
Date: Wed, 15 Dec 2010 17:22:13 -0800
Message-Id: <F1F326CF-412C-42CE-BB7B-6C57A5688B9D@gmail.com>
Cc: Christoph Päper <christoph.paeper@crissov.de>, www-style list <www-style@w3.org>
To: "Tab Atkins Jr." <jackalmage@gmail.com>



Brad Kemper

On Dec 15, 2010, at 4:13 PM, "Tab Atkins Jr." <jackalmage@gmail.com> wrote:

> On Wed, Dec 15, 2010 at 2:10 PM, Christoph Päper
> <christoph.paeper@crissov.de> wrote:
>> Tab Atkins Jr.:
>>> 
>>> The relationship between image pixels and CSS px are defined by the image-resolution property, which defaults to 1dppx (1 dot per px). That is, each image pixel is a CSS px.
>> 
>> Yes, that’‚ a good thing, but the property should default to ‘1px’ and authors should be able to set it to ‘1dot’ (or ‘1mm’ or ‘1in’). That means it should not use new reciprocal units.
> 
> The unit used is an editorial issue.  The spec already allows authors
> to set the resolution in 'in' or 'cm' using the 'dpi' and 'dpcm'
> units.
> 
> I'm not sure how you could base the resolution on dots, considering
> that you're defining the size of the dots.
> 
> 
> That said, does anyone actually implement 'image-resolution' yet?  It
> does seem sort of silly to define resolution units that are just
> inverted length units.  We could just use length units instead, and
> avoid the headache I get every time I mentally parse "dppx" (my brain
> insists on first trying to interpret the "dpp" as "device pixels per"
> and then the "x" just makes the whole thing seize up).

When thinking about resolution, I always think in terms of dpi. It is what printers and other output devices were measured in for as long as I can remember, and how image resolution is set in PhotoShop. I imagine that in other parts of the world (I'm in the US), dpcm might have been more common. So I think the 'dp' part is pretty much a gimme, and 'dppx' flows naturally out of that. 
Received on Thursday, 16 December 2010 01:22:56 GMT

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