如何用php生成扭曲及旋转的验证码图片

<?php 
function make_rand($length="32"){//验证码文字生成函数 
        $str="abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890"; 
    $result=""; 
    for($i=0;$i<$length;$i++){ 
        $num[$i]=rand(0,61); 
        $result.=$str[$num[$i]]; 
    } 
    return $result; 
} 
$checkcode = make_rand(5); 
$im_x=160; 
$im_y=32; 
function make_crand($length="5") { 
    $string = ''; 
    for($i=0;$i<$length;$i++) { 
        $string .= chr(rand(0xB0,0xF7)).chr(rand(0xA1,0xFE)); 
    } 
    return $string; 
} 
function getAuthImage($text , $im_x = 230 , $im_y = 32) { 
    $im = imagecreatetruecolor($im_x,$im_y); 
    $text_c = ImageColorAllocate($im, mt_rand(0,100),mt_rand(0,100),mt_rand(0,100)); 
    $tmpC0=mt_rand(100,255); 
    $tmpC1=mt_rand(100,255); 
    $tmpC2=mt_rand(100,255); 
    $buttum_c = ImageColorAllocate($im,$tmpC0,$tmpC1,$tmpC2); 
    imagefill($im, 16, 13, $buttum_c); 
    //echo $text; 
    $font = 'c://WINDOWS//Fonts//simsun.ttc'; 
    //echo strlen($text); 
    $text=iconv("gb2312","UTF-8",$text); 
    //echo mb_strlen($text,"UTF-8"); 
    for ($i=0;$i<mb_strlen($text);$i++) 
    { 
            $tmp =mb_substr($text,$i,1,"UTF-8"); 
            $array = array(-1,0,1); 
            $p = array_rand($array); 
            $an = $array[$p]*mt_rand(1,9);//角度 
            $size = 20; 
            imagettftext($im,$size,$an,10+$i*$size*2,25,$text_c,$font,$tmp); 
    } 
     $distortion_im = imagecreatetruecolor ($im_x, $im_y); 
     imagefill($distortion_im, 16, 13, $buttum_c); 
     for ( $i=0; $i<$im_x; $i++) { 
         for ( $j=0; $j<$im_y; $j++) { 
             $rgb = imagecolorat($im, $i , $j); 
             if( (int)($i+20+sin($j/$im_y*2*M_PI)*10) <= imagesx($distortion_im) && (int)($i+20+sin($j/$im_y*2*M_PI)*10) >=0 ) { 
                 imagesetpixel ($distortion_im, (int)($i+10+sin($j/$im_y*2*M_PI-M_PI*0.5)*3) , $j , $rgb); 
             } 
         } 
     } 
     //加入干扰象素; 
    $count = 600;//干扰像素的数量 
    for($i=0; $i<$count; $i++){ 
            $randcolor = ImageColorallocate($distortion_im,mt_rand(0,255),mt_rand(0,255),mt_rand(0,255)); 
            imagesetpixel($distortion_im, mt_rand()%$im_x , mt_rand()%$im_y , $randcolor); 
    } 
    $line_c=5; 
     //imageline 
     for($i=0; $i < $line_c; $i++) { 
         $linecolor = imagecolorallocate($distortion_im, 17, 158, 20); 
         $lefty = mt_rand(1, $im_x-1); 
         $righty = mt_rand(1, $im_y-1); 
         imageline($distortion_im, 0, $lefty, imagesx($distortion_im), $righty, $linecolor); 
     } 
     Header("Content-type: image/PNG"); 
    //以PNG格式将图像输出到浏览器或文件; 
    //ImagePNG($im); 
    ImagePNG($distortion_im); 
    //销毁一图像,释放与image关联的内存; 
    ImageDestroy($distortion_im); 
    ImageDestroy($im); 
} 
?>

<?php
getAuthImage(make_crand(5)); 
?>