Image Captcha Ajax

A.
This module only provide two http/ajax api:

1).
Initialize the captcha session firstly:

URL : http://localhost/ajax/image_captcha_sid
return the captcha image url and the sid.
2).
get captcha image src
URL: http://localhost/ajax/image_captcha_img/[sid]

B.
Another simple way:
The client only request the URL:

http://localhost/ajax/image_captcha?refresh=[timestamp]
this url will generate the captcha image, and will save sid to cookie automatically, refresh the url will regenerate the image also.

Validate:
use this function,

  function image_captcha_ajax_validate_captcha($solution = NULL, $sid = NULL);