Pure PHP CAPTCHA: Generate CAPTCHA images without using GD extension

This class can Generate CAPTCHA images without using GD extension.

It extends the PureTextRender class to generate an image with a random text with a given length.

The text in the image is scaled, rotated, and distorted to make it more difficult for automated scripts recognized the text.

The class returns the rendered text string for posterior validation.

The base class generates the image as the current script output in pure PHP, i.e. without using GD or any other PHP extensions to generate images.