[whatwg] add html-attribute for "responsive images"

[Kornel Lesiński]

On Wed, 08 Feb 2012 09:06:36 -0000, David Goss <dvdgoss at gmail.com> wrote:

>> When browser has a high-quality image the cached already, but media  
>> query for "network-connection: gprs" matches, it would be shame to  
>> force it to
>> switch to a lousy image.
>
> True. But that's mostly likely to happen on a phone, where its most
> unlikley to have a high-quality image cached in the first place.

I use RSS reader which preloads all images when I'm on Wi-Fi, but I read  
those feeds when I'm on the go, and often even off-line (BTW: which media  
query would match off-line?)

I would be disappointed if my phone supported media queries that tell it  
to discard high-quality images it has preloaded and spend extra time  
downloading worse versions.

> It's not just about size or speed though. For
> example, your layout might be different in landscape than in portrait,
> so you might want a different aspect ratio version of the image.

I agree with that, and I think these may be two distinct use-cases, which  
are best served by different solutions.

If image has different ratio and/or is cropped differently for purpose of  
page's layout, then it's important for the browser to respect that —  
that's part of the design, and that has been an artistic decision by the  
page author.

But selection between heavily compressed and higher-fidelity version of  
the same image (with same ratio, same content) is just an optimisation. It  
doesn't require authors' judgement. Selection of the version can be  
expressed by an algorithm, and it's fine for the browser to pick  
higher-resolution image if it has it in the cache, rather than respect  
media queries exactly as written.

It's also orthogonal to the layout issue — you may want to have landscape  
and portrait versions of the image for both regular and high-dpi displays  
(or slow and fast networks).

So instead of combination of four media queries (which would get quite  
verbose if you were going to take into account several factors, not just  
network speed) I think it would be better to combine two very simple media  
queries for orientation with simple declaration of adaptive image  
resolution (that makes browser automatically take into account screen  
size/density and network speed, without needing details spelled out by the  
page author).

-- 
regards, Kornel Lesiński