How to use Photon to serve custom cropped Post thumbnails

The Photon module resizes your site’s images on the fly, without cropping them. However, in some cases you might want Photon to apply a custom cropping when resizing certain images. In the following example, we will use photon to serve Post thumbnails with custom cropping, and use a different cropping on single pages:

if( function_exists( 'jetpack_photon_url' ) ) {
    add_filter( 'jetpack_photon_url', 'jetpack_photon_url', 10, 3 );
}
function jeherve_display_custom( $content, $post ) {

	global $post;

	// If you didn't define a post thumnail, let's forget about all this
	if ( !has_post_thumbnail( $post->ID ) )
		return $content;

	// What's the cropping and the size of image we should use on Single pages?
	// See http://developer.wordpress.com/docs/photon/api/#crop for parameters
	if ( is_single() ) {
		$args = array(
		    'crop'   => '50,50,200px,200px',
		);
	}
	// resizing on other pages
	else {
		$args = array(
		    'resize'   => '200,400',
		);
	}

	// Let's create a Photon Image URL from the Post Thumbnail
	$feat_image_url = wp_get_attachment_image_src( get_post_thumbnail_id($post->ID), 'full');
	$photon_image_url = jetpack_photon_url( $feat_image_url[0], $args );

	// Let's build the image tag
	$our_image = sprintf( '<div class="post-media"><a class="featured-image" href="%1$s" title="%2$s"><img src="%3$s" class="wp-post-image" alt="Featured Image"></a></div>',
		esc_url( get_permalink() ),
		esc_attr( sprintf( __( 'Open %s', 'dot' ), get_the_title() ) ),
		esc_attr( $photon_image_url )
	);

	// Let's return the image, right before the post content
	return $our_image . $content;

}
add_filter( 'the_content', 'jeherve_display_custom' );

Reference