<picture>
  <source srcset="<?php echo wp_get_attachment_image_url($img_id, '1440x480'); ?> 1x, <?php echo wp_get_attachment_image_url($img_id, '2880x960'); ?> 2x" media="(min-width: 992px)">
  <source srcset="<?php echo wp_get_attachment_image_url($img_id, '990x300'); ?> 1x, <?php echo wp_get_attachment_image_url($img_id, '1980x600'); ?> 2x" media="(min-width: 768px)">
  <source srcset="<?php echo wp_get_attachment_image_url($img_id, '760x300'); ?> 1x, <?php echo wp_get_attachment_image_url($img_id, '1520x600'); ?> 2x" media="(min-width: 576px)">
  <source srcset="<?php echo wp_get_attachment_image_url($img_id, '570x250'); ?> 1x, <?php echo wp_get_attachment_image_url($img_id, '1140x500'); ?> 2x" media="(max-width: 575px)">
  <img src="<?php echo wp_get_attachment_image_url($img_id, '1440x480'); ?>" alt="">
</picture>