PHP imagecreatefrombmp 从BMP文件或URL新建一图像

大家都知道php gd库可方便的从url新建一图像, gd中有imagecreatefromjpeg()，imagecreatefrompng()....等之类的function 可有时从url中读取的切bmp图像而 可恨的是 gd2中切偏偏没有imagecreatefrombmp() 虽然有imagecreatefromwbmp() 但还是相差还是很远！
用下面function可以方便解决

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++)
{
$c=freadbits($f,$bibitcount);
imagesetpixel($img,$x,$y,$palette[$c]);
}
if($currentbit!=0) {freadbyte($f);}
for($g=0;$g<$zbytek;$g++)
freadbyte($f);
}
}
}
if($rlecompression==1) //$bi_rle8
{
$y=$height;
$pocetb=0;
while(true)
{
$y--;
$prefix=freadbyte($f);
$suffix=freadbyte($f);
$pocetb+=2;
$echoit=false;
if($echoit)echo "prefix: $prefix suffix: $suffix<br>";
if(($prefix==0)and($suffix==1)) break;
if(feof($f)) break;
while(!(($prefix==0)and($suffix==0)))
{
if($prefix==0)
{
$pocet=$suffix;
$data.=fread($f,$pocet);
$pocetb+=$pocet;
if($pocetb%2==1) {freadbyte($f); $pocetb++;}
}
if($prefix>0)
{
$pocet=$prefix;
for($r=0;$r<$pocet;$r++)
$data.=chr($suffix);
}
$prefix=freadbyte($f);
$suffix=freadbyte($f);
$pocetb+=2;
if($echoit) echo "prefix: $prefix suffix: $suffix<br>";
}
for($x=0;$x<strlen($data);$x++)
{
imagesetpixel($img,$x,$y,$palette[ord($data[$x])]);
}
$data="";
}
}
if($rlecompression==2) //$bi_rle4
{
$y=$height;
$pocetb=0;
/*while(!feof($f))
echo freadbyte($f)."_".freadbyte($f)."<br>";*/
while(true)
{
//break;
$y--;
$prefix=freadbyte($f);
$suffix=freadbyte($f);
$pocetb+=2;
$echoit=false;
if($echoit)echo "prefix: $prefix suffix: $suffix<br>";
if(($prefix==0)and($suffix==1)) break;
if(feof($f)) break;
while(!(($prefix==0)and($suffix==0)))
{
if($prefix==0)
{
$pocet=$suffix;
$currentbit=0;
for($h=0;$h<$pocet;$h++)
$data.=chr(freadbits($f,4));
if($currentbit!=0) freadbits($f,4);
$pocetb+=ceil(($pocet/2));
if($pocetb%2==1) {freadbyte($f); $pocetb++;}
}
if($prefix>0)
{
$pocet=$prefix;
$i=0;
for($r=0;$r<$pocet;$r++)
{
if($i%2==0)
{
$data.=chr($suffix%16);
}
else
{
$data.=chr(floor($suffix/16));
}
$i++;
}
}
$prefix=freadbyte($f);
$suffix=freadbyte($f);
$pocetb+=2;
if($echoit) echo "prefix: $prefix suffix: $suffix<br>";
}
for($x=0;$x<strlen($data);$x++)
{
imagesetpixel($img,$x,$y,$palette[ord($data[$x])]);
}
$data="";
}
}
if($bibitcount==24)
{
$img=imagecreatetruecolor($width,$height);
$zbytek=$width%4;
for($y=$height-1;$y>=0;$y--)
{
for($x=0;$x<$width;$x++)
{
$b=freadbyte($f);
$g=freadbyte($f);
$r=freadbyte($f);
$color=imagecolorexact($img,$r,$g,$b);
if($color==-1) $color=imagecolorallocate($img,$r,$g,$b);
imagesetpixel($img,$x,$y,$color);
}
for($z=0;$z<$zbytek;$z++)
freadbyte($f);
}
}
return $img;
}
fclose($f);
}
function freadbyte($f)
{
return ord(fread($f,1));
}
function freadword($f)
{
$b1=freadbyte($f);
$b2=freadbyte($f);
return $b2*256+$b1;
}
function freaddword($f)
{
$b1=freadword($f);
$b2=freadword($f);
return $b2*65536+$b1;
}