Select rendered picture element image in chrome

I have a need to re-use the rendered image of a picture element. Is there a direct way to use javascript to access the image file path rendered by chrome/opera without having to replicate the logic that picturefill completes.

<picture>
  <source media="(min-width: 800px)" srcset="head.jpg, head-2x.jpg 2x">
  <source media="(min-width: 450px)" srcset="head-small.jpg, head-small-2x.jpg 2x">
  <img src="head-fb.jpg" srcset="head-fb-2x.jpg 2x" >
</picture>

Using the example above, on a retina desktop browser window with a width of 1200px, a browser with picture support will render head-2x.jpg. Or, if I'm using chrome browser on a smart phone with width less than 450px with retina display, it would use head-fb-2x.jpg. How can I access this dynamically rendered image directly?

Is there a way to access this rendered image without having to parse the source elements myself?

There is the currentSrc proprety, which is only updated, if the candidate was loaded. A function could look something like this:

function getCurrentSrc(element, cb){
    var getSrc;
    if(!window.HTMLPictureElement){
        if(window.respimage){
            respimage({elements: [element]});
        } else if(window.picturefill){
            picturefill({elements: [element]});
        }
        cb(element.src);
        return;
    }

    getSrc = function(){
        element.removeEventListener('load', getSrc);
        element.removeEventListener('error', getSrc);
        cb(element.currentSrc);
    };

    element.addEventListener('load', getSrc);
    element.addEventListener('error', getSrc);
    if(element.complete){
        getSrc();
    }
}

Note: you have to pass the img DOM element and a callback function.