中文：使用SIMSUN即可
$graph->title->SetFont(FF_SIMSUN,FS_NORMAL,10);
UTF-8：改代码才行
jpgraph_ttf.inc.php，在99到106行之间，全部注释掉
elseif( $aFF === FF_SIMSUN ) {
// Do Chinese conversion
if( $this->g2312 == null ) {
include_once 'jpgraph_gb2312.php' ;
$this->g2312 = new GB2312toUTF8();
}
return $this->g2312->gb2utf8($aTxt);
}
