RainCaptcha is a CAPTCHA class that does not require any image processing extensions (GD, ImageMagick, etc). CAPTCHA was developed to be readable by humans and resistant to OCR software. It generates black-and-white images with 5 distorted letters on them and noise. Its checking algorithm is case-insensitive.
Blur effect is an object that can apply the blur effect to HTML page elements. It takes the identifier of a given page element and starts an animation effect that progressively alters CSS properties of that element that make it appear blurred. Different CSS properties may be altered depending on the capabilities of the current browser. The object can also execute an animation that reverts the blur effect of the element. There are versions of the object either based or not in the jQuery library.
The captcha.php library is very user-friendly and extremely easy to integrate into existing forms, because of its simple API. It nevertheless sports many configuration options, like multiple image modes and accessible alternative text riddles. It also has "AJAX" super cow powers and many sensible defaults to frustrate users less than other implementations. It prevents spambot access well, even with its relaxed defaults.