Visual Composer adds ?id= to background images of columns and rows - php

Question

I'm trying to speed up a WordPress website which uses Visual Composer plugin. In GTmetrix result I see this:
Serve resources from a consistent URL
https://example.com/wp-content/uploads/2015/02/sfondo_form.jpg?id=15129
The image with query string ?id=XXX is background of a column in Visual Composer. How can I disable it?
All these queries are in the VC custom shortcode. Check the picture below:

Answer 1

In case that might be helpful to anyone - I modified regex query to fetch all background styles:
$value = preg_replace('/(url\(\S+\.(jpg|jpeg|png|svg|gif))\?id=\d+(\))/', '$1$3', $value);

Answer 2

Background styles save in post_meta table. Here is how VC add custom CSS in a page body:
$shortcodes_custom_css = get_post_meta( $id, '_wpb_shortcodes_custom_css', true );
if ( ! empty( $shortcodes_custom_css ) ) {
$shortcodes_custom_css = strip_tags( $shortcodes_custom_css );
echo '<style type="text/css" data-type="vc_shortcodes-custom-css">';
echo $shortcodes_custom_css;
echo '</style>';
}
So we can filter post_meta value and VC output as we want:
add_filter('get_post_metadata', 'theme_prefix_vc_fix_shortcodes_custom_css', 10, 4);
function theme_prefix_vc_fix_shortcodes_custom_css($value, $object_id, $meta_key, $single) {
if ($meta_key!='_wpb_shortcodes_custom_css' || is_admin()) {
return $value;
}
// filter data for _wpb_shortcodes_custom_css only and not for admin
remove_filter('get_post_metadata', 'theme_prefix_vc_fix_shortcodes_custom_css', 10);
$value = get_metadata('post', $object_id, $meta_key, $single);
// we need to remove filter here because get_metadata function use "get_post_metadata" hook so we will have loop if not remove filter
if ($value) {
// you can use another regular expression, this is what I created quickly
$value = preg_replace("/(background-image[:\s]+url\(\S+\.(jpg|jpeg|png|svg|gif))\?id=\d+(\))/", "$1$3", $value);
}
add_filter('get_post_metadata', 'theme_prefix_vc_fix_shortcodes_custom_css', 10, 4);
return $value;
}
Alternatively, you can use the_content filter to remove ?id=XXXX from background images in document body.