Override captcha library class in magento 2
It is not so complicated. First in composer.json
file add this line in psr-0
node
"Zend_Captcha": "app/code/"
so it will look like that
"psr-0": {
"": "app/code/",
"Zend_Captcha": "app/code/"
},
Then create directory app/code/Zend/Captcha/
and place there your file Image.php
that you want to override.
After that just run composer update
.