Beans: simple responsive images example.

functions.php

<?php
// Do not include the opening php tag if it is already included in your file.

add_action( 'beans_post_body_prepend_markup', 'beans_child_reponsive_image_sample' );

function beans_child_reponsive_image_sample() {

	$src = 'http://images.apple.com/euro/ipad-mini-4/a/screens_alt/images/overview/hero_large.png';
	$small = beans_edit_image( $src, array(
		'resize' => array( 465, false ),
	), 'OBJECT' );
	$medium = beans_edit_image( $src, array(
		'resize' => array( 650, false )
	), 'OBJECT' );

	?>
	<picture>
		<source media="(max-width: <?php echo $small->width; ?>px)" srcset="<?php echo $small->src; ?>">
		<source media="(max-width: <?php echo $medium->width; ?>px)" srcset="<?php echo $medium->src; ?>">
		<img src="<?php echo $src; ?>" alt="a cute kitten">
	</picture>
	<?php

}