EllisLab/CodeIgniter — pull request #3020 by afk11 (2014-04-23 02:04:37+00:00)
Title: Optionally output captcha images in base64 encoding.

Adding the 'base64' entry to the $defaults array (set to FALSE). If the base64 key in $data is set to FALSE, the image will be converted to base64 without being written to disk, allowing the library to work on read only file systems.