Really Simple CAPTCHA does not work anymore since wordpress 5.2

Hello Takayuki,
Really Simple CAPTCHA does not work since WP 5.2. Here is the error reported by WP:

Hello!

Since WordPress 5.2, a native feature allows you to detect if an extension or theme causes a fatal error on your site, and notifies you with this automatic email.

Here, WordPress found an error with one of your extensions, “Really Simple CAPTCHA”.

XXXXXX

Details of the error
======================
An error of type E_ERROR was caused in line 127 of the file /home/villaclafk/www/wp-content/plugins/really-simple-captcha/really-simple-captcha.php. Error Message: Uncaught Error: Call to undefined function imagettftext() in /home/villaclafk/www/wp-content/plugins/really-simple-captcha/really-simple-captcha.php:127
Stack trace:
#0 /home/villaclafk/www/wp-content/plugins/contact-form-7/modules/really-simple-captcha.php(501): ReallySimpleCaptcha->generate_image(1667405780, ‘VFP4’)
#1 /home/villaclafk/www/wp-content/plugins/contact-form-7/modules/really-simple-captcha.php(62): wpcf7_generate_captcha(Array)
#2 /home/villaclafk/www/wp-content/plugins/contact-form-7/includes/form-tags-manager.php(340): wpcf7_captchac_form_tag_handler(Object(WPCF7_FormTag))
#3 /home/villaclafk/www/wp-content/plugins/contact-form-7/includes/form-tags-manager.php(269): WPCF7_FormTagsManager->scan_callback(Array, true)
#4 [internal function]: WPCF7_FormTagsManager->replace_callback(Array)
#5 /home/villaclafk/www/wp-content/plugins/contact-form-7/includes/form-tags-manager.php(186): preg_replace_callback(‘/(\\[?)\\[(accept…’, Array, ‘Quelle locat…’)
#6 /home/villaclafk/www/wp-content/plugin

I hope you can help me.
Best regards,
Lionel