PHP读取BMP格式图片的函数

PHP中居然没有读取BMP格式图片的函数,还好高人已经写好一个,我没看代码,反正能正常使用.
imagecreatefrombmp -- 从 BMP 文件或 URL 新建一图像
function imagecreatefrombmp($file)
{
global $CurrentBit, $echoMode;
$f=fopen($file,"r");
$Header=fread($f,2);
if($Header=="BM")
{
$Size=freaddword($f);
$Reserved1=freadword($f);
$Reserved2=freadword($f);
$FirstByteOfImage=freaddword($f);
$SizeBITMAPINFOHEADER=freaddword($f);
$Width=freaddword($f);
$Height=freaddword($f);
$biPlanes=freadword($f);
$biBitCount=freadword($f);
$RLECompression=freaddword($f);
$WidthxHeight=freaddword($f);
$biXPelsPerMeter=freaddword($f);
$biYPelsPerMeter=freaddword($f);
$NumberOfPalettesUsed=freaddword($f);
$NumberOfImportantColors=freaddword($f);
if($biBitCount<24)
{
$img=imagecreate($Width,$Height);
$Colors=pow(2,$biBitCount);
for($p=0;$p<$Colors;$p++)
{
$B=freadbyte($f);
$G=freadbyte($f);
$R=freadbyte($f);
$Reserved=freadbyte($f);
$Palette[]=imagecolorallocate($img,$R,$G,$B);
}

if($RLECompression==0)
{
$Zbytek=(4-ceil(($Width/(8/$biBitCount)))%4)%4;
for($y=$Height-1;$y>=0;$y--)
{
$CurrentBit=0;
for($x=0;$x<$Width;$x++)