Get details about available image sizes - WordPress

/**
 * Get all the registered image sizes along with their dimensions
 *
 * @global array $_wp_additional_image_sizes
 *
 * @link http://core.trac.wordpress.org/ticket/18947 Reference ticket
 *
 * @return array $image_sizes The image sizes
 */
function _get_all_image_sizes() {
	global $_wp_additional_image_sizes;

	$default_image_sizes = get_intermediate_image_sizes();

	foreach ( $default_image_sizes as $size ) {
		$image_sizes[ $size ][ 'width' ] = intval( get_option( "{$size}_size_w" ) );
		$image_sizes[ $size ][ 'height' ] = intval( get_option( "{$size}_size_h" ) );
		$image_sizes[ $size ][ 'crop' ] = get_option( "{$size}_crop" ) ? get_option( "{$size}_crop" ) : false;
	}

	if ( isset( $_wp_additional_image_sizes ) && count( $_wp_additional_image_sizes ) ) {
		$image_sizes = array_merge( $image_sizes, $_wp_additional_image_sizes );
	}

	return $image_sizes;
}

Array
(
	[thumbnail] => Array
		(
			[width] => 150
			[height] => 150
			[crop] => 1
		)

	[medium] => Array
		(
			[width] => 300
			[height] => 300
			[crop] => 
		)

	[medium_large] => Array
		(
			[width] => 768
			[height] => 0
			[crop] => 
		)

	[large] => Array
		(
			[width] => 1024
			[height] => 1024
			[crop] => 
		)

)