Thanks, Ernest! The example you provide works great if in the ACF settings the return format is set to ‘Image ID’. In my case it was ‘Image Array’ so I modified the code a bit:
add_filter( 'asp_results', 'asp_get_main_prod_img', 10, 1 );
function asp_get_main_prod_img($results) {
$acf_image_field = 'design_image';
$size = 'medium';
foreach ( $results as $k => &$r ) {
if ( empty($r->image) && function_exists('get_field') ) {
$image_array = get_field( $acf_image_field, $r->id );
if ( count( $image_array ) > 0 && array_key_exists( 'sizes', $image_array ) ) {
$img = $image_array['sizes'][$size];
if ( isset( $img ) && !is_wp_error( $img ) )
$r->image = $img;
}
}
}
return $results;
}Thank you for the help!