to create an image from a BMP file, I made this function, that return a resource like the others ImageCreateFrom function:
<?php
function ImageCreateFromBMP($filename)
{
 if (! $f1 = fopen($filename,"rb")) return FALSE;
 $FILE = unpack("vfile_type/Vfile_size/Vreserved/Vbitmap_offset", fread($f1,14));
   if ($FILE['file_type'] != 19778) return FALSE;
 $BMP = unpack('Vheader_size/Vwidth/Vheight/vplanes/vbits_per_pixel'.
                 '/Vcompression/Vsize_bitmap/Vhoriz_resolution'.
                 '/Vvert_resolution/Vcolors_used/Vcolors_important', fread($f1,40));
   $BMP['colors'] = pow(2,$BMP['bits_per_pixel']);
   if ($BMP['size_bitmap'] == 0) $BMP['size_bitmap'] = $FILE['file_size'] - $FILE['bitmap_offset'];
   $BMP['bytes_per_pixel'] = $BMP['bits_per_pixel']/8;
   $BMP['bytes_per_pixel2'] = ceil($BMP['bytes_per_pixel']);
   $BMP['decal'] = ($BMP['width']*$BMP['bytes_per_pixel']/4);
   $BMP['decal'] -= floor($BMP['width']*$BMP['bytes_per_pixel']/4);
   $BMP['decal'] = 4-(4*$BMP['decal']);
   if ($BMP['decal'] == 4) $BMP['decal'] = 0;
 $PALETTE = array();
   if ($BMP['colors'] < 16777216)
   {
    $PALETTE = unpack('V'.$BMP['colors'], fread($f1,$BMP['colors']*4));
   }
 $IMG = fread($f1,$BMP['size_bitmap']);
   $VIDE = chr(0);
   $res = imagecreatetruecolor($BMP['width'],$BMP['height']);
   $P = 0;
   $Y = $BMP['height']-1;
   while ($Y >= 0)
   {
    $X=0;
    while ($X < $BMP['width'])
    {
     if ($BMP['bits_per_pixel'] == 24)
        $COLOR = unpack("V",substr($IMG,$P,3).$VIDE);
     elseif ($BMP['bits_per_pixel'] == 16)
     {  
        $COLOR = unpack("n",substr($IMG,$P,2));
        $COLOR[1] = $PALETTE[$COLOR[1]+1];
     }
     elseif ($BMP['bits_per_pixel'] == 8)
     {  
        $COLOR = unpack("n",$VIDE.substr($IMG,$P,1));
        $COLOR[1] = $PALETTE[$COLOR[1]+1];
     }
     elseif ($BMP['bits_per_pixel'] == 4)
     {
        $COLOR = unpack("n",$VIDE.substr($IMG,floor($P),1));
        if (($P*2)%2 == 0) $COLOR[1] = ($COLOR[1] >> 4) ; else $COLOR[1] = ($COLOR[1] & 0x0F);
        $COLOR[1] = $PALETTE[$COLOR[1]+1];
     }
     elseif ($BMP['bits_per_pixel'] == 1)
     {
        $COLOR = unpack("n",$VIDE.substr($IMG,floor($P),1));
        if     (($P*8)%8 == 0) $COLOR[1] =  $COLOR[1]        >>7;
        elseif (($P*8)%8 == 1) $COLOR[1] = ($COLOR[1] & 0x40)>>6;
        elseif (($P*8)%8 == 2) $COLOR[1] = ($COLOR[1] & 0x20)>>5;
        elseif (($P*8)%8 == 3) $COLOR[1] = ($COLOR[1] & 0x10)>>4;
        elseif (($P*8)%8 == 4) $COLOR[1] = ($COLOR[1] & 0x8)>>3;
        elseif (($P*8)%8 == 5) $COLOR[1] = ($COLOR[1] & 0x4)>>2;
        elseif (($P*8)%8 == 6) $COLOR[1] = ($COLOR[1] & 0x2)>>1;
        elseif (($P*8)%8 == 7) $COLOR[1] = ($COLOR[1] & 0x1);
        $COLOR[1] = $PALETTE[$COLOR[1]+1];
     }
     else
        return FALSE;
     imagesetpixel($res,$X,$Y,$COLOR[1]);
     $X++;
     $P += $BMP['bytes_per_pixel'];
    }
    $Y--;
    $P+=$BMP['decal'];
   }
 fclose($f1);
 return $res;
}
?>