首先, 先到這兒抓取 Better Captcha. 抓回解開之後, 把 fonts 這個目錄放到 authimage 的目錄下頭. 然後修改 pluginauthimage.class.php 如下:

--- authimage.old/pluginauthimage.class.php	2006-07-05 10:19:57.000000000 +0800
+++ authimage/pluginauthimage.class.php	2006-10-16 14:20:28.744067612 +0800
@@ -8,7 +8,10 @@
 
     define( "AUTHIMAGE_FILE", "/plugins/authimage/authimage.php" );
     define( "AUTHIMAGE_BACKGROUND_FOLDER", PLOG_CLASS_PATH."plugins/authimage/backgrounds/" );
-    
+// twu2 20061016 begin
+    define( "AUTHIMAGE_FONT_FOLDER", PLOG_CLASS_PATH."plugins/authimage/fonts/" );
+// twu2 20061016 end
+
     /**
      * Plugin that offers comment authentication image for current blog
      * Original Author: Gudlyf http://www.gudlyf.com/index.php?p=376
@@ -93,8 +96,9 @@
 
         function show() {
             $authImageUrl = $this->generateImageUrl();
+                //return '<img src="'.$authImageUrl.'" style="vertical-align:middle;" width="70px" height="20px" alt="authimage" />'; 
             if ( $authImageUrl )
-                return '<img src="'.$authImageUrl.'" style="vertical-align:middle;" width="70px" height="20px" alt="authimage" />'; 
+                return '<img src="'.$authImageUrl.'" style="vertical-align:middle;" alt="authimage" />'; 
             else
                 return 'You don\'t have GD support compiled in, we cannot create an authimage. Please activate GD Support.';
         }
@@ -103,6 +107,16 @@
             // Delete those cached authimage files that never used
             $this->deleteExpiredAuthImage($this->expiredTime);
             
+// twu2 20061016 begin
+            $code = $this->generateCode();
+            $encrypt = $this->encrypt($code, $this->key);
+            if ( function_exists ( 'ImageGIF' ) ) 
+		$image_format = 'gif';
+	    else
+		$image_format = 'png';
+            $tempFile = $this->cacheFolder."/".$encrypt.".".$image_format;
+	    $this->captcha_createimage($code, $image_format, $tempFile);
+/* old method for image
             $code = $this->generateCode();
             $encrypt = $this->encrypt($code, $this->key);
             $background = AUTHIMAGE_BACKGROUND_FOLDER.$this->default;
@@ -125,6 +139,8 @@
             } else {
                 ImageGIF($image, $tempFile);
             }
+*/
+// twu2 20061016 end
             $temp = fopen($tempFile,"rb");
             $buffer = fread($temp,filesize($tempFile));
             fclose($temp);
@@ -137,7 +153,10 @@
             // Now chmod it so it can be deleted later by the user
             chmod($tempFile, 0666);
             
-            header("Content-type: image/gif");
+// twu2 20061016 begin
+            //header("Content-type: image/gif");
+            header("Content-type: image/".$image_format);
+// twu2 20061016 end
             echo $buffer;
         }
 
@@ -150,7 +169,14 @@
         	
         function generateCode() {
             $code = "";
-            for($i=0; $i < $this->length; $i++) $code .= rand(0,9);
+// twu2 20061016 begin
+            //for($i=0; $i < $this->length; $i++) $code .= rand(0,9);
+	    //$hash = "0123456789";
+	    //$hash = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
+	    $hash = "0123456789ABCDEFGHKMNPQRWXYZ";
+	    $len = strlen($hash) - 1;
+            for($i=0; $i < $this->length; $i++) $code .= $hash[rand(0,$len)];
+// twu2 20061016 end
             return $code;
         }        
         
@@ -168,6 +194,135 @@
                 closedir($handle); 
             }
         }           
+
+// twu2 20061016 begin
+        function captcha_createimage($code, $image_format, $tempFile)
+        {
+            $breedte = rand(256, 384);
+            $hoogte = rand(64, 96);
+            $img = imagecreatetruecolor($breedte,$hoogte);
+            $achtergrond = imagecolorallocate($img, $this->captcha_color("bg"), $this->captcha_color("bg"), $this->captcha_color("bg")); 			
+
+            imagefilledrectangle($img, 0, 0, $breedte-1, $hoogte-1, $achtergrond); 
+	    $hash = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
+	    $hash_len = strlen($hash);
+            for($g = 0;$g < 30; $g++)
+            {
+		$t = $hash[rand(0, $hash_len)];
+                    
+                $ypos = rand(0,$hoogte);
+                $xpos = rand(0,$breedte);
+                    
+                $kleur = imagecolorallocate($img, $this->captcha_color("bgtekst"), $this->captcha_color("bgtekst"), $this->captcha_color("bgtekst"));
+
+                if (!($g % 2))
+   		{
+		      $scribx = rand(0,($breedte*2));
+		      $scriby = rand(0,($hoogte*2));                     
+      
+		      $wibblex = rand(0,($breedte*2));
+		      $wibbley = rand(0,($hoogte*2));
+      
+		      imageline($img, rand(0, $scribx-$xpos), rand(0, $scriby+$ypos), rand(0, $wibblex), rand(0, $wibbley), $kleur+$g);
+		      imageellipse($img, rand(0, $scribx+$xpos), rand(0, $scriby-$ypos), rand(0, $scriby), rand(0, $scribx), $kleur-$g);             
+		}
+                    
+                imagettftext($img, $this->captcha_size(), $this->captcha_move(), $xpos, $ypos, $kleur, $this->captcha_font(), $t);
+            } 			
+            $stukje = $breedte / (strlen($code) + 3);
+
+            for($j = 0;$j < strlen($code); $j++)
+            {
+                $tek = $code[$j];
+                $ypos = rand(32,$hoogte-8);
+                $xpos = $stukje * ($j+2);
+                    
+                $kleur2 = imagecolorallocate($img, $this->captcha_color("tekst"), $this->captcha_color("tekst"), $this->captcha_color("tekst"));
+                
+                imagettftext($img, $this->captcha_size(), $this->captcha_move(), $xpos, $ypos, $kleur2, $this->captcha_font() , $tek);
+            }
+                
+	    if ($image_format == 'gif')
+                imagegif($img, $tempFile);
+	    else
+                imagepng($img, $tempFile);
+            imagedestroy($img); 			
+        }
+
+        /**
+          * Some functions :)
+          * Also orginally written by mastercode.nl
+          **/
+        /**
+          * Function to create a random color
+          * @auteur mastercode.nl
+          * @param $type string Mode for the color
+          * @return int
+          **/
+        function captcha_color($type)
+        {
+            switch($type)
+            {
+                case "bg": 
+                    $kleur = rand(224,255); 
+                break;
+                case "tekst": 
+                    $kleur = rand(0,127); 
+                break;
+                case "bgtekst": 
+                    $kleur = rand(200,224); 
+                break;
+                default: 
+                    $kleur = rand(0,255); 
+                break;
+            }
+            return $kleur;
+        }
+        /**
+          * Function to ranom the size
+          * @auteur mastercode.nl
+          * @return int
+          **/
+        function captcha_size()
+        {
+            $grootte = rand(24,32);
+            return $grootte;
+        }
+        /**
+          * Function to random the posistion
+          * @auteur mastercode.nl
+          * @return int
+          **/
+        function captcha_move()
+        {
+            $draai = rand(-25,25);
+            return $draai;
+        }
+        /**
+          * Function to return a ttf file from fonts map
+          * @auteur mastercode.nl
+          * @return string
+          **/
+        function captcha_font()
+        {
+            $f = @opendir(AUTHIMAGE_FONT_FOLDER);
+            $ar = array();
+            while(($file = @readdir($f)) !== false)
+            {
+                if(!in_array($file,array('.','..')) && eregi('.ttf',$file))
+                {
+                    $ar[] = $file;
+                }
+            }
+            if(count($ar))
+            {
+                shuffle($ar);
+                $i = rand(0,(count($ar) - 1));
+                return AUTHIMAGE_FONT_FOLDER . $ar[$i];
+            }
+        }    
+// twu2 20061016 end
+
     }
         
 ?>
 

patch 可以到這兒抓: http://www.teatime.com.tw/~tommy/mypatch/lifetype_authimage_better_captcha.patch

我修改了 generateCode() 的部份, 讓出現的字串為數字與大寫的英文字母, 但是把其中幾個比較容易弄錯的字母移除. 如果你想修改出現的字串, 請修改這個 function 內的 $hash 變數值就可以.