当我使用get_the_post_thumbnail( NULL, \'entry-fullwidth\', NULL ); wordpress自动输出srcset 以下数据：

<img 
    width="1000" 
    height="625" 
    src="https://x.cloudfront.net/wp-content/uploads/2017/08/photo.jpg" 
    class="attachment-entry-fullwidth size-entry-fullwidth wp-post-image" 
    alt="" 
    srcset="
        https://x.cloudfront.net/wp-content/uploads/2017/08/photo.jpg 1000w, 
        https://x.cloudfront.net/wp-content/uploads/2017/08/photo-768x480.jpg 768w" 
    sizes="
        (max-width: 767px) 95vw, 
        (max-width: 979px) 80vw, 1200px
">

在下面的自定义函数中，是否有本机wordpress函数或其他方式输出图像的srcset数据？

function photo_shortcode($atts){
   extract(shortcode_atts(array(
      \'no\' => 1,
   ), $atts));

   $no     = ( $no       != \'\'     ) ? $no : 1;
   $images = get_field(\'fl_gallery\');
   $image  = $images[$no];

if ($image) {
   $credit = get_field(\'fl_credit\', $image[\'id\']);
   return \'<div class="kalim"><img title="\' . esc_attr( sprintf( the_title_attribute( \'echo=0\' ) ) ) . \'" alt="\' . esc_attr( sprintf( the_title_attribute( \'echo=0\' ) ) ) . \'" src="\' . $image[\'url\'] . \'" /><div class="kalca">\' . $image[\'caption\'] . \'</div>\' . (!empty($credit) ? \'<div class="kalcr">Credit:\' . $credit . \'</div></div>\': \'\' ) ;
 }

}

add_shortcode(\'photo\', \'photo_shortcode\');

$srcset = wp_get_attachment_image_srcset( $image[\'id\'], array( 100, 100 ) );

<img src="PATH HERE" srcset="<?php echo esc_attr( $srcset ); ?>">