在GD中输出汉字的函数的改进

感谢sadly为我们写出了在GD中输出汉字的函数，
我在使用中发现此版本输出的字符串必须为纯中文，不能夹杂英文。
随修改了此bug，与大家分享。。。

<?
//Program writen by sadly www.phpx.com
//modified by agun 2000/6/20
function gb2utf8($gb)
{
if(!trim($gb))
return $gb;
$filename="gb2312.txt";
$tmp=file($filename);
$codetable=array();
while(list($key,$value)=each($tmp))
$codetable[hexdec(substr($value,0,6))]=substr($value,7,6);

$ret="";
$utf8="";
while($gb)
{
if (ord(substr($gb,0,1))>127)
{
$this=substr($gb,0,2);
$gb=substr($gb,2,strlen($gb));
$utf8=u2utf8(hexdec($codetable[hexdec(bin2hex($this))-0x8080]));
for($i=0;$i<strlen($utf8);$i+=3)
$ret.=chr(substr($utf8,$i,3));
}
else
{
$ret.=substr($gb,0,1);
$gb=substr($gb,1,strlen($gb));
}
}
return $ret;
}

function u2utf8($c)
{
for($i=0;$i<count($c);$i++)
$str="";
if ($c <0x80) {
$str.=$c;
}
else if ($c <0x800) {
$str.=(0xC0 | $c>>6);
$str.=(0x80 | $c & 0x3F);
}
else if ($c <0x10000) {
$str.=(0xE0 | $c>>12);
$str.=(0x80 | $c>>6 & 0x3F);
$str.=(0x80 | $c & 0x3F);
}
else if ($c <0x200000) {
$str.=(0xF0 | $c>>18);
$str.=(0x80 | $c>>12 & 0x3F);
$str.=(0x80 | $c>>6 & 0x3F);
$str.=(0x80 | $c & 0x3F);
}
return $str;
}

Header("Content-type: image/gif");
$im = imagecreate(300,150);
$bkg = ImageColorAllocate($im, 0,0,0);
$clr = ImageColorAllocate($im, 255,255,255);
$fnt = "c:windowsfontssimsun.ttf";
//include("gb2utf8.php");
$str = gb2utf8("中国agun阿棍");
ImageTTFText($im, 30, 0, 50,50, $clr, $fnt, $str);
ImageGif($im);
ImageDestroy($im);
?>