中文验证码类

public function str_cn($width, $height, $len = 3, $size = 12)
        {
        	$string = '';
		    for($i=0;$i<$len;$i++) {
		        $string .= chr(rand(0xB0,0xF7)).chr(rand(0xA1,0xFE));
		    } 
            $this->out_put_cnniuqu($string);
        }
        
        public function out_put_cnniuqu($text , $im_x = 160 , $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 $text;
        		<span style="color:#FF0000;">$font = MIO_PATH.'/Font/msyh.ttf';</span>
        		//echo strlen($text);
        		<span style="color:#FF0000;">$text=iconv("gb2312","UTF-8",$text);</span>
        		<span style="color:#FF0000;">$_SESSION['verify'] = $text;</span>
        		//echo mb_strlen($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(4,11);//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, $linecolor);
        	}
        	<span style="color:#FF0000;">ob_clean();</span>
        	Header("Content-type: image/PNG");
        	//以PNG格式将图像输出到浏览器或文件;
        	//ImagePNG($im);
        	ImagePNG($distortion_im);
        	//销毁一图像,释放与image关联的内存;
        	ImageDestroy($distortion_im);
        	ImageDestroy($im);
        }

转自：http://www.jb51.net/article/38071.htm

稍做修改以适用linux,注意带上字体哦。