Stretchy images shouldn't require media queries

Hello all,

I just sent a big email to the WHATWG list, using a srcset example to
illustrate the pitfalls of tying a responsive-images markup solution to
viewport-size queries. Requiring authors to bake information about their
layouts into their markup results in markup that is potentially complex and
certianly fragile.

http://lists.whatwg.org/pipermail/whatwg-whatwg.org/2012-November/037772.html

All of my concerns also apply to <picture>. Replace my "this is complex and
fragile" srcset example with this:

<picture>

<source media="(min-width: 56em)" srcset="400.jpg 1x, 800.jpg 2x">
<source media="(min width: 32em)" srcset="200.jpg 1x, 400.jpg 2x">
<source media="(min-width: 28em)" src="800.jpg">
<source srcset="400.jpg 1x, 800.jpg 2x">
 <img src="200.jpg">

</picture>


....and the "just let authors describe the resources" example with this:


<picture>

<source src="800.jpg" width="800" height="533">
<source src="400.jpg" width="400" height="266">
<source src="200.jpg" width="200" height="133">

<img src="200.jpg">

</picture>


....and it's an email about the <picture> spec. Thoughts?

—eric