Remove sources (thumbnails) from the srcset array

functions.php.php

<?php

add_filter( 'wp_calculate_image_srcset', 'child_hero_image_srcset', 10, 5 );
/**
 * Remove sources from the srcset array
 * Only use large and above
 *
 * @link https://www.smashingmagazine.com/2016/09/responsive-images-in-wordpress-with-art-direction/
 */
function child_hero_image_srcset( $sources, $size_array, $image_src, $image_meta, $attachment_id ) {

    /*
    Original srcset
    image-300x188.jpg 300w,
    image-768x480.jpg 768w,
    image-1024x640.jpg 1024w,
    image-1536x960.jpg 1536w,
    image-2048x1280.jpg 2048w,
    image.jpg 2560w
    */

    if ( is_front_page() && ( $attachment_id == '57664' ) ) {

        // get cutoff as width of the largest cropped image size
        // (in HTML, breakpoint = cutoff + 1 )
        $cutoff = $image_meta['sizes']['medium_large']['width'];

        // check if our version is the full-sized version by
        // comparing its width to the cutoff
        if ( $cutoff < $size_array[0] ) {

            // for each element in tentative srcset
            foreach ( $sources as $key => $value ) {

                // if image width is at or below cutoff,
                // we don't need it
                if ( $cutoff >= $key ) {
                    unset( $sources[ $key ] );
                }

            }

        }

    }
    return $sources;

}