captcha_non_gd.php

这些都是我以前学习是用到的源码

<?php
/** 
*
* @package VC
* @version $Id: captcha_non_gd.php,v 1.6 2006/11/15 15:34:33 acydburn Exp $
* @copyright (c) 2006 phpBB Group 
* @license http://opensource.org/licenses/gpl-license.php GNU Public License 
*
*/


/**
* Main non-gd captcha class
* @ignore
* @package VC
*/
class captcha
{
	var $filtered_pngs;
	var $width = 320;
	var $height = 50;

	/**
	* Define filtered pngs on init
	*/
	function captcha()
	{
		// If we can we will generate a single filtered png, we avoid nastiness via emulation of some Zlib stuff
		$this->define_filtered_pngs();
	}

	/**
	* Create the image containing $code
	*/
	function execute($code)
	{
		$img_height = $this->height - 10;
		$img_width = 0;

		list($usec, $sec) = explode(' ', microtime()); 
		mt_srand($sec * $usec);

		$char_widths = $hold_chars = array();
		$code_len = strlen($code);

		for ($i = 0; $i < $code_len; $i++)
		{
			$char = $code[$i];

			$width = mt_rand(0, 4);
			$raw_width = $this->filtered_pngs[$char]['width'];
			$char_widths[$i] = $width;
			$img_width += $raw_width - $width;

			// Split the char into chunks of $raw_width + 1 length
			if (empty($hold_chars[$char]))
			{
				$hold_chars[$char] = str_split(base64_decode($this->filtered_pngs[$char]['data']), $raw_width + 1);
			}
		}

		$offset_x = mt_rand(0, $this->width - $img_width);
		$offset_y = mt_rand(0, $this->height - $img_height);

		$image = '';
		for ($i = 0; $i < $this->height; $i++)
		{
			$image .= chr(0);