W3C home > Mailing lists > Public > public-respimg@w3.org > February 2013

Re: CfC: to publish "The srcset attribute" specification as a First Public Working Draft (FPWD)

From: Mathew Marquis <mat@matmarquis.com>
Date: Tue, 5 Feb 2013 07:46:32 -0500
Cc: "Paul.Cotton@microsoft.com" <paul.cotton@microsoft.com>, "public-html-admin@w3.org" <public-html-admin@w3.org>, "public-respimg@w3.org" <public-respimg@w3.org>
Message-Id: <0C1C5125-7F54-465E-BE28-745957BCEB60@matmarquis.com>
To: Fred Andrews <fredandw@live.com>
On Tuesday, Feb 5, 2013, at 12:30 AM, Fred Andrews wrote:

> Perhaps the problem needs to defined in even simpler terms.
> Given the input string "image_200x100.jpg 1x, image_400x200.jpg 2x"
> and a target image box size of 20x10 or 60x30 or 100x50 or
> 200x100 or 300x150 or 400x200 or 800x400 or 1920x960 device
> pixels please supply a computation that selects the smallest
> image that gives a sharp presentation?
> The answers:
> 20x10: image_200x100.jpg
> 60x20: image_200x100.jpg
> 100x50: image_200x100.jpg
> 200x100: image_200x100.jpg
> 300x150: image_400x200.jpg
> 400x200: image_400x200.jpg
> 800x400: image_400x200.jpg
> 1920x960: image_400x200.jpg
> Another example: given the input string "image_300x150.jpg 1x,
> image_600x300.jpg 2x" and the same target image box sizes?

Wait, so you’re talking about *contextually-aware* image selection based on the size of the containing element? I guess this is the root of the confusion—this isn’t a use case we’ve aimed to solve, and there hasn’t been call for it. Unfortunately, this use case would also be impossible to accommodate: the UA doesn’t have information about the layout available at the time the images are [pre]fetched.

Any flags on either element dealing with sizing or resolution are in reference to the client’s *display*, similar to (or using) media queries. Choosing the image source size most appropriate for a container always 50% of the available screen will require consideration on the part of the author, as they must do currently with layout elements and CSS media query breakpoints.

I apologize for the confusion.

> [ snip ]

Received on Tuesday, 5 February 2013 12:47:01 UTC

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