What is the GD library?
GD is an open source code library for the dynamic creation of images by programmers. GD is written in C, and “wrappers” are available for Perl, PHP and other languages. GD creates PNG, JPEG and GIF images, among other formats. GD is commonly used to generate charts, graphics, thumbnails, and most anything else, on the fly. While not restricted to use on the web, the most common applications of GD involve website development.
Hope this clears things up?
The captcha is an image with mostly numbers. If GD library is not enabled, that could cause this kind of issues, but most of the time it is already enabled and so in this case it seems this is not the cause of our issue eather.
Hope this clears things up?