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.
<?php
function bmp2gd($src, $dest = false) {
if(!($src_f = fopen($src, "rb"))) return false;
if(!($dest_f = fopen($dest, "wb"))) return false;
$header = unpack("vtype/Vsize/v2reserved/Voffset", fread($src_f, 14));
$info = unpack("Vsize/Vwidth/Vheight/vplanes/vbits/Vcompression/Vimagesize/Vxres/Vyres/Vncolor/Vimportant", fread($src_f, 40));
extract($info);
extract($header);
if($type != 0x4D42) return false;
$palette_size = $offset-54;
$ncolor = $palette_size/4;
$gd_header = "";
$gd_header .= ($palette_size == 0) ? "\xFF\xFE" : "\xFF\xFF";
$gd_header .= pack("n2", $width, $height);
$gd_header .= ($palette_size == 0) ? "\x01" : "\x00";
if($palette_size) $gd_header .= pack("n", $ncolor);
$gd_header .= "\xFF\xFF\xFF\xFF";
fwrite($dest_f, $gd_header);
if($palette_size) {
$palette = fread($src_f, $palette_size);
$gd_palette = "";
$j = 0;
while($j < $palette_size) {
$b = $palette{$j++};
$g = $palette{$j++};
$r = $palette{$j++};
$a = $palette{$j++};
$gd_palette .= "$r$g$b$a";
}
$gd_palette .= str_repeat("\x00\x00\x00\x00", 256-$ncolor);
fwrite($dest_f, $gd_palette);
}
$scan_line_size = (($bits * $width) + 7) >> 3;
$scan_line_align = ($scan_line_size & 0x03) ? 4 - ($scan_line_size & 0x03) : 0;
for($i = 0, $l = $height -1; $i < $height; $i++, $l--) {
fseek($src_f, $offset + (($scan_line_size + $scan_line_align) * $l));
$scan_line = fread($src_f, $scan_line_size);
if($bits == 24) {
$gd_scan_line = "";
$j = 0;
while($j < $scan_line_size) {
$b = $scan_line{$j++};
$g = $scan_line{$j++};
$r = $scan_line{$j++};
$gd_scan_line .= "\x00$r$g$b";
}
} else if($bits == 8) {
$gd_scan_line = $scan_line;
} else if($bits == 4) {
$gd_scan_line = "";
$j = 0;
while($j < $scan_line_size) {
$byte = ord($scan_line{$j++});
$p1 = chr($byte >> 4);
$p2 = chr($byte & 0x0F);
$gd_scan_line .= "$p1$p2";
}
$gd_scan_line = substr($gd_scan_line, 0, $width);
} else if($bits == 1) {
$gd_scan_line = "";
$j = 0;
while ($j < $scan_line_size) {
$byte = ord($scan_line{$j++});
$p1 = chr((int) (($byte & 0x80) != 0));
$p2 = chr((int) (($byte & 0x40) != 0));
$p3 = chr((int) (($byte & 0x20) != 0));
$p4 = chr((int) (($byte & 0x10) != 0));
$p5 = chr((int) (($byte & 0x08) != 0));
$p6 = chr((int) (($byte & 0x04) != 0));
$p7 = chr((int) (($byte & 0x02) != 0));
$p8 = chr((int) (($byte & 0x01) != 0));
$gd_scan_line .= "$p1$p2$p3$p4$p5$p6$p7$p8";
}
$gd_scan_line = substr($gd_scan_line, 0, $width);
}
fwrite($dest_f, $gd_scan_line);
}
fclose($src_f);
fclose($dest_f);
return true;
} function imagecreatefrombmp($filename) {
$tmp_name = tempnam("tmp", "BMP");
if(bmp2gd($filename, $tmp_name)) {
$img = imagecreatefromgd($tmp_name);
unlink($tmp_name);
return $img;
}
return false;
}
?>
