Responsive images based on the 'picture' element proposal. See http://picture.responsiveimages.org/.

##Why?

• Browser support: Tested in IE 6-9, Chrome, Firefox, Opera, Safari, iOS and Android
• Speed: Uses native or polyfilled matchMedia to evaluate each <span data-media="..." />
• Size: 2.27KB minified (1.02KB gzipped)

###Picture example patterns

#####noscript fallback which requires data-alt attribute on data-picture element.

<span data-picture data-alt="img alt">
    <span data-media="(min-width: 1000px)" data-srcset="lib/my_high.jpg 1x, lib/my_high_2x.jpg 2x"></span>
    <span data-media="(min-width: 800px)" data-src="lib/my_medium.jpg"></span>
    <span data-media="(min-width: 400px)" data-src="lib/my_low.jpg"></span>
    <span data-srcset="lib/my_low.jpg 1x, lib/my_high.jpg 2x"></span>

    <noscript>
        <img src="lib/my_low.jpg" alt="my fallback content" />
    </noscript>
</span>

#####img fallback with the lowest size/quality src which does not require data-alt attribute on data-picture element as long as it is present on the img element.

<span data-picture>
    <span data-media="(min-width: 1000px)" data-srcset="lib/my_high.jpg 1x, lib/my_high_2x.jpg 2x"></span>
    <span data-media="(min-width: 800px)" data-src="lib/my_medium.jpg"></span>
    <span data-media="(min-width: 400px)" data-src="lib/my_low.jpg"></span>
    <span data-srcset="lib/my_low.jpg 1x, lib/my_high.jpg 2x"></span>

    <img src="lib/my_low.jpg" alt="img alt" />
</span>

#####noscript fallback which requires data-alt attribute on data-picture element. data-picture element has data-srcset attribute.

<span data-picture data-srcset="lib/my_high.jpg 1x, lib/my_high_2x.jpg 2x" data-alt="img alt">
    <noscript>
        <img src="lib/my_low.jpg" alt="my fallback content" />
    </noscript>
</span>

#####img fallback with the lowest size/quality src which does not require data-alt attribute on data-picture element as long as it is present on the img element. data-picture element has data-srcset attribute.

<span data-picture data-srcset="lib/my_high.jpg 1x, lib/my_high_2x.jpg 2x">
    <img src="lib/my_low.jpg" alt="img alt" />
</span>

#####noscript fallback which requires data-alt attribute on data-picture element. data-picture element has data-src attribute.

<span data-picture data-src="lib/my_high.jpg" data-alt="img alt">
    <noscript>
        <img src="lib/my_low.jpg" alt="my fallback content" />
    </noscript>
</span>

#####img fallback with the lowest size/quality src which does not require data-alt attribute on data-picture element as long as it is present on the img element. data-picture element has data-src attribute.

<span data-picture data-src="lib/my_high.jpg">
    <img src="lib/my_low.jpg" alt="img alt" />
</span>

We've chosen to use a span as our picture element because it's not as common as divs, meaning it will be faster when requesting an element collection and return less results to loop over.

Fallback for users without javascript enabled will see the noscript content.

###Future improvements

• Supported v2.2.0 picture data-srcset attribute support (supercedes src attribute and source elements)
• Supported v2.2.0 picture data-src attribute support (supercedes source elements)
• Supported v2.2.0 source data-srcset attribute support
• Supported v2.2.0 Content negotiation based on the previous 3 ways of setting image content
• picture data-media attribute support (currently matched media query)
• Supported v2.2.0 picture data-current-src attribute support (current src url)
• picture data-width attribute support
• picture data-height attribute support

###Dependencies None, unless a polyfill is required for window.matchMedia with listener support. If your project requires support of IE <= 9 or iOS <= 5.0 or Opera <= 12, try https://github.com/weblinc/media-match. It's another of our projects focused on performance, near full CSS3 feature support and broad browser compatibility.