How to get the best image resolution from srcset in WordPress post? For example, the image code looks like this:

    <img src="/uploads/2012/12/Multitronics-TC-750-300x175.jpg"
 class="aligncenter size-medium wp-image-3280 lazyloaded"
 alt="Multitronics TC 750"
 srcset="/uploads/2012/12/Multitronics-TC-750-300x175.jpg 300w, /uploads/2012/12/Multitronics-TC-750-513x265.jpg 513w, /uploads/2012/12/Multitronics-TC-750.jpg 1260w"
 sizes="(max-width: 300px) 100vw, 300px">

How to get the maximum image size (like Multitronics-TC-750.jpg 1260w) using the function? For example wp_calculate_image_srcset ()?