Chinese display in graphic functions

Convert the GB code to UTF8. TTF in php supports UTF8-encoded non-ASCII character output. After analyzing this code, it is found that it can be implemented to mix the output image with Chinese and ASCII, which can be more convenient when we operate the image function.
The code is as follows:
<?

function gb2utf8($gb)
{
if(!trim($gb))
return $gb;
$filename="";
$tmp=file($filename);
$codetable=array();
while(list($key,$value)=each($tmp))
$codetable[hexdec(substr($value,0,6))]=substr($value,7,6);

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

/*$ret="";
for($i=0;$i<strlen($utf8);$i+=3)
$ret.=chr(substr($utf8,$i,3));

return $ret;*/

return $utf8;
}
function u2utf8($c)
{
/*for($i=0;$i<count($c);$i++)*/
$str="";
if ($c < 0x80) {
$str.=$c;
}
else if ($c < 0x800) {
$str.=chr(0xC0 | $c>>6);
$str.=chr(0x80 | $c & 0x3F);
}
else if ($c < 0x10000) {
$str.=chr(0xE0 | $c>>12);
$str.=chr(0x80 | $c>>6 & 0x3F);
$str.=chr(0x80 | $c & 0x3F);
}
else if ($c < 0x200000) {
$str.=chr(0xF0 | $c>>18);
$str.=chr(0x80 | $c>>12 & 0x3F);
$str.=chr(0x80 | $c>>6 & 0x3F);
$str.=chr(0x80 | $c & 0x3F);
}
return $str;
}
?>


--------------------------------------------
<?
Header ("Content-type: image/jpeg");
$im = imagecreate (800, 400);
$black = ImageColorAllocate ($im, 0, 0, 0);
$white = ImageColorAllocate ($im, 255, 255, 255);
include("");
$str=gb2utf8("aaa passed 32434");
ImageTTFText ($im, 90, 10, 110, 300, $white, "/usr/share/fonts/default/TrueType/",
$str);

ImageJPEG ($im);
ImageDestroy ($im);

?>