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);
}
}