Wordpress automatically adds srcset and sizes attributes to all images coming from posts. That’s very neat.
But how to I get WordPress to add those attributes to images that come from a customizer input?
In my case: a default image for posts. That default image is displayed when no image was uploaded in a post. It’s uploaded by the user through the customizer and called using get_theme_mod.
image from post (works fine, all attributes are added):
get_the_post_thumbnail($post->ID, 'news', array('class' => 'img-responsive'));
if no image is provided: the default image is loaded (no ’scrset’ and ’sizes’)
'<img src="' . esc_url( get_theme_mod( 'default_image' ) ) . '" alt="default image" class="img-responsive" />'
wp_image_add_srcset_and_sizes() seems to be the way to go but it requires attributes I don’t know where to get.
Thank you for your help!