How to change the captcha.lib

My captcha images and text are very hard to see.

would someone help me to modify the script a little to make it bold and get the slanty lines out of the middle.

<?php
# ----------------------------------------------------
// DO NOT EDIT
require_once("config.php");
error_reporting(E_ALL );
function Get_Text()
{
global $text_length;
	$letters =  array("a","A","b","B","c","C","d","D","e","E","f","F","g","G",
"h","H","i","I","j","J","k",
"K","l","L","m","M","n","N","o","O","p","P","q","Q","r",
"R","s","S","t","T","u","U","v",
"V","w","W","x","X","y","Y","z","Z","1","2","3","4","5",
"6","7","8","9");
mt_srand((double)microtime()*1000000);
 $txt = "";
 //$rand_keys = array_rand($letters, $text_length);
 //foreach($rand_keys as $key)
// {
 // $txt .= $letters[$key];
// }
shuffle($letters);
for($i=0;$i<$text_length;$i++)
{
  $key = rand(0,count($letters)-1);
  $txt .= $letters[$key];	
}
return $txt;
}

function create_image()
{
    global $width,$hight,$text_length,$border;
    $im = imagecreate($width,$hight);
    $bgc = imagecolorallocate($im, rand(235,255), rand(235,255),rand(235,255));
    $tc  = imagecolorallocate($im, 0, 0, 0);
    imagefill($im,0,0,$tc);
    imagefilledrectangle($im,$border,$border,$width-$border,$hight-$border,$bgc);
    return $im;

}

function draw_string($txt,$im)
{
   global $hight,$width,$font,$text_length;
   $space1 = $width/($text_length+1);   //space between characters
   $space2 = ($width - $space1)/3  ;   //space between lines
   $center = $hight/2;


   for($f=0;$f<3;$f++)
   {
   	$y1 =  $center/2;
  	$y2 =  1.5*$center;
  	$x1 = ($space1/2) + ($f * $space2);
  	$x2 = ($space1/2) + (($f +1) * $space2);
  	// echo "$x1,$x2 + $y1,$y2 <br>";
     for($k=0;$k<2;$k++)
	  {
           $lc =  imagecolorallocate($im,rand(0,200), rand(0,200), rand(0,200));
           imageline($im,rand($x1,$x2),rand($y1,$y2),rand($x1,$x2),rand($y1,$y2),$lc);
      }
    }

	for($i=0;$i<$text_length;$i++)
	{
	 $txtc =  imagecolorallocate($im,rand(0,160), rand(0,160), rand(0,160));
	 $x = ($space1+($i*$space1)); //x  coordinate of each character
	 
	 imagestring($im,$font,$x,rand($center-($center/2),$center),$txt[$i],$txtc);
	}

}
?>

PHP:

<?php
// DO NOT EDIT
session_start();
error_reporting(E_ALL ^ E_NOTICE);
require_once("captchalib.php");
header("Content-type: image/png");

$str = Get_Text();
$im = create_image();
draw_string($str,$im);
imagepng($im);
if($CaseSenstive==true)
{
$_SESSION['pfw_text']=md5($str);
}
else
{
$str = strtolower($str);
$_SESSION['pfw_text']=md5($str);
}
?>

PHP:

<?php
//this file includes the settings of form captcha
$error = 'security code is not correct'  ;
$error_display_mode = 2 ;
$error_page=  '' ;
$font =  5  ;
$hight = 40  ;
$width =  120  ;
$text_length = 3  ;
$border =  0  ;

//Make sure you change this to refelct the proper contact form name.
$form =  contact.htm'  ;
$CaseSenstive = false  ;
$user = 'max'  ;
$pass =  'dde2790ce930e3d425305c36afd4e69c' ;
$redirect = false ;
$success_page = 'thank-you.htm'  ;
?>

PHP:

 

First of all try to change the $font.

 

tried that already...it worked somewhat
I want to get rid of those pesky slanted lines on image.