<?php if(extension_loaded('gd')) {   echo '你可以使用gd<br>';   foreach(gd_info() as $cate=>$value)     echo "$cate: $value<br>"; }else   echo '你没有安装gd扩展'; ?>

<?php /**  * vCode(m,n,x,y) m个数字  显示大小为n   边宽x   边高y  * 自己改写记录session $code  */ session_start(); vCode(4, 15); //4个数字，显示大小为15 function vCode($num = 4, $size = 20, $width = 0, $height = 0) {  !$width && $width = $num * $size * 4 / 5 + 5;  !$height && $height = $size + 10;  // 去掉了 0 1 O l 等  $str = "23456789abcdefghijkmnpqrstuvwxyzABCDEFGHIJKLMNPQRSTUVW";  $code = '';  for ($i = 0; $i < $num; $i++) {   $code .= $str[mt_rand(0, strlen($str)-1)];  }  // 画图像  $im = imagecreatetruecolor($width, $height);  // 定义要用到的颜色  $back_color = imagecolorallocate($im, 235, 236, 237);  $boer_color = imagecolorallocate($im, 118, 151, 199);  $text_color = imagecolorallocate($im, mt_rand(0, 200), mt_rand(0, 120), mt_rand(0, 120));  // 画背景  imagefilledrectangle($im, 0, 0, $width, $height, $back_color);  // 画边框  imagerectangle($im, 0, 0, $width-1, $height-1, $boer_color);  // 画干扰线  for($i = 0;$i < 5;$i++) {   $font_color = imagecolorallocate($im, mt_rand(0, 255), mt_rand(0, 255), mt_rand(0, 255));   imagearc($im, mt_rand(- $width, $width), mt_rand(- $height, $height), mt_rand(30, $width * 2), mt_rand(20, $height * 2), mt_rand(0, 360), mt_rand(0, 360), $font_color);  }  // 画干扰点  for($i = 0;$i < 50;$i++) {   $font_color = imagecolorallocate($im, mt_rand(0, 255), mt_rand(0, 255), mt_rand(0, 255));   imagesetpixel($im, mt_rand(0, $width), mt_rand(0, $height), $font_color);  }  // 画验证码  @imagefttext($im, $size , 0, 5, $size + 3, $text_color, 'c:\WINDOWS\Fonts\simsun.ttc', $code);  $_SESSION["VerifyCode"]=$code;  header("Cache-Control: max-age=1, s-maxage=1, no-cache, must-revalidate");  header("Content-type: image/png;charset=gb2312");  imagepng($im);  imagedestroy($im); } ?>

//首先开启session session_start(); //定义前台显示验证码长&宽 $image_width = 120; $image_height = 40; $characters_on_image = 6; $font = './monofont.ttf'; //The characters that can be used in the CAPTCHA code. //avoid confusing characters (l 1 and i for example) $possible_letters = '23456789bcdfghjkmnpqrstvwxyz'; $random_dots = 10; $random_lines = 30; $captcha_text_color="0x142864"; $captcha_noice_color = "0x142864"; //定义要生成验证码的字符串 $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); /* setting the background, text and noise colours here */ $background_color = imagecolorallocate($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']); /* generating the dots randomly in background */ for( $i=0; $i<$random_dots; $i++ ) { imagefilledellipse($image, mt_rand(0,$image_width),  mt_rand(0,$image_height), 2, 3, $image_noise_color); } /* generating lines randomly in background of image */ for( $i=0; $i<$random_lines; $i++ ) { imageline($image, mt_rand(0,$image_width), mt_rand(0,$image_height),  mt_rand(0,$image_width), mt_rand(0,$image_height), $image_noise_color); } /* create a text box and add 6 letters code in it */ $textbox = imagettfbbox($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 , $code); /* Show captcha image in the page html page */ header('Content-Type: image/jpeg');// defining the image type to be shown in browser widow imagejpeg($image);//showing the image imagedestroy($image);//destroying the image instance //设置session，做验证 $_SESSION['6_letters_code'] = $code; function hexrgb ($hexstr) {   $int = hexdec($hexstr);   return array("red" => 0xFF & ($int >> 0x10),                "green" => 0xFF & ($int >> 0x8),                "blue" => 0xFF & $int); }