Images in PDF displays as a red cross (https / mpdf)

First  please make sure, that you are not on a localhost AND do not have any .htaccess / .passwd on your sever. Because our plugin uses HTTP to get the images for the PDF creation and if your server blocks the images from public it won’t work.

Problem not solves? Read further:

Please make sure you have installed / configured the following in your Server PHP Extensions:

  1. CURL Enabled (php_curl.dll enabled)
  2. PHP.ini (allow_url_fopen = On)
  3. GD Library installed

To debug image loading go to plugin settings > advanced settings. There enable the MPDF Debug mode:

MPDF debug mode
MPDF debug mode

Look what the image errors show. Maybe you find the issue yourself.

If images still do not display you can solve the issue by the following ways:

Quick and Dirty:

Add the following to the mpdf.php file on line 12954 -> function: file_get_contents_by_curl()

curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);



The better solution is to manually add only the certificate(s) or CA(s) you want to accept

; php.ini Options  ;

curl.cainfo = "C:\xampp\php\extras\ssl\cacert.pem"


On Nginx?

Some nginx server disallow some agents in the CURL header. Therefore you will need to change the header. Go to plugin-folder/includes/mpdf/mpdf.php > Line: 12965.

Then change the CURLOPT_USERAGENT value to ‘User-Agent: curl/7.39.0’


curl_setopt($ch, CURLOPT_USERAGENT, 'User-Agent: curl/7.39.0');

2 thoughts on “Images in PDF displays as a red cross (https / mpdf)

  1. Rodrigo Murillo says:

    We resolved it. Your help article would be greatly improved if you suggest the following:

    $this->mpdf->showImageErrors = true;
    $this->mpdf->debug = true;

    Add that to link 279 build_pdf() in class-woocommerce-pdf-catalog-public.php

    once that was added the PHP debug log showed:

    Jan 03 08:33:26 ip-10-0-36-166 debug: [03-Jan-2018 16:33:22 UTC] PHP Fatal error: Uncaught MpdfException: IMAGE Error (https://XXX/file.png): Could not find image file in /var/www/wordpress/htdocs/wp-content/woocommerce-pdf-catalog/includes/mpdf/mpdf.php:11752

    this showed us the error was related to a DNS issue locally:

    curl https://XXX/file.png
    curl: (6) Could not resolve host:

    Once we saw that error, the problem was obvious

    Thanks for the assistance –

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