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session_start();

//设置: 你可以在这里修改验证码图片的参数

$image_width = 120;

$image_height = 40;

$characters_on_image = 6;

$font = ‘./monofont.ttf’;

//以下字符将用于验证码中的字符

//为了避免混淆去掉了数字1和字母i

$possible_letters = ‘23456789bcdfghjkmnpqrstvwxyz’;

$random_dots = 10;

$random_lines = 30;

$captcha_text_color=”0x142864″;

$captcha_noice_color = “0x142864”;

$code = ”;

$i = 0;

while ($i < $characters_on_image) {

$code .= substr($possible_letters, mt_rand(0, strlen($possible_letters)-1), 1);

$i++;

}

$font_size = $image_height * 0.75;

$image = @imagecreate($image_width, $image_height);

/* 设置背景、文本和干扰的噪点 */

$background_color = imagecolorallocate($image, 255, 255, 255);

$arr_text_color = hexrgb($captcha_text_color);

$text_color = imagecolorallocate($image, $arr_text_color[‘red’],

$arr_text_color[‘green’], $arr_text_color[‘blue’]);

$arr_noice_color = hexrgb($captcha_noice_color);

$image_noise_color = imagecolorallocate($image, $arr_noice_color[‘red’],

$arr_noice_color[‘green’], $arr_noice_color[‘blue’]);

/* 在背景上随机的生成干扰噪点 */

for( $i=0; $i

imagefilledellipse($image, mt_rand(0,$image_width),

mt_rand(0,$image_height), 2, 3, $image_noise_color);

}

/* 在背景图片上，随机生成线条 */

for( $i=0; $i

imageline($image, mt_rand(0,$image_width), mt_rand(0,$image_height),

mt_rand(0,$image_width), mt_rand(0,$image_height), $image_noise_color);

}

/* 生成一个文本框，然后在里面写生6个字符 */

$textbox = imagettfbbox($font_size, 0, $font, $code);

$x = ($image_width – $textbox[4])/2;

$y = ($image_height – $textbox[5])/2;

imagettftext($image, $font_size, 0, $x, $y, $text_color, $font , $code);

/* 将验证码图片在HTML页面上显示出来 */

header(‘Content-Type: image/jpeg’);

// 设定图片输出的类型

imagejpeg($image);

//显示图片

imagedestroy($image);

//销毁图片实例

$_SESSION[‘6_letters_code’] = $code;

function hexrgb ($hexstr) {

$int = hexdec($hexstr);

return array( “red” => 0xFF & ($int >> 0x10),

“green” => 0xFF & ($int >> 0x8),

“blue” => 0xFF & $int

);

}

?>

验证码