php imagecreatefrombmp

function imagecreatefrombmp($filename) {
	// version 1.00
	if (!($fh = fopen($filename, 'rb'))) {
		trigger_error('imagecreatefrombmp: Can not open ' . $filename, E_USER_WARNING);
		return false;
	}
	// read file header
	$meta = unpack('vtype/Vfilesize/Vreserved/Voffset', fread($fh, 14));
	// check for bitmap
	if ($meta['type'] != 19778) {
		trigger_error('imagecreatefrombmp: ' . $filename . ' is not a bitmap!', E_USER_WARNING);
		return false;
	}
	// read image header
	$meta += unpack('Vheadersize/Vwidth/Vheight/vplanes/vbits/Vcompression/Vimagesize/Vxres/Vyres/Vcolors/Vimportant', fread($fh, 40));
	// read additional 16bit header
	if ($meta['bits'] == 16) {
		$meta += unpack('VrMask/VgMask/VbMask', fread($fh, 12));
	}
	// set bytes and padding
	$meta['bytes'] = $meta['bits'] / 8;
	$meta['decal'] = 4 - (4 * (($meta['width'] * $meta['bytes'] / 4)- floor($meta['width'] * $meta['bytes'] / 4)));
	if ($meta['decal'] == 4) {
		$meta['decal'] = 0;
	}
	// obtain imagesize
	if ($meta['imagesize'] < 1) {
		$meta['imagesize'] = $meta['filesize'] - $meta['offset'];
		// in rare cases filesize is equal to offset so we need to read physical size
		if ($meta['imagesize'] < 1) {
			$meta['imagesize'] = @filesize($filename) - $meta['offset'];
			if ($meta['imagesize'] < 1) {
				trigger_error('imagecreatefrombmp: Can not obtain filesize of ' . $filename . '!', E_USER_WARNING);
				return false;
			}
		}
	}
	// calculate colors
	$meta['colors'] = !$meta['colors'] ? pow(2, $meta['bits']) : $meta['colors'];
	// read color palette
	$palette = array();
	if ($meta['bits'] < 16) {
		$palette = unpack('l' . $meta['colors'], fread($fh, $meta['colors'] * 4));
		// in rare cases the color value is signed
		if ($palette[1] < 0) {
			foreach ($palette as $i => $color) {
				$palette[$i] = $color + 16777216;
			}
		}
	}
	// create gd image
	$im = imagecreatetruecolor($meta['width'], $meta['height']);
	$data = fread($fh, $meta['imagesize']);
	$p = 0;
	$vide = chr(0);
	$y = $meta['height'] - 1;
	$error = 'imagecreatefrombmp: ' . $filename . ' has not enough data!';
	// loop through the image data beginning with the lower left corner
	while ($y >= 0) {
		$x = 0;
		while ($x < $meta['width']) {
			switch ($meta['bits']) {
				case 32:
				case 24:
					if (!($part = substr($data, $p, 3))) {
						trigger_error($error, E_USER_WARNING);
						return $im;
					}
					$color = unpack('V', $part . $vide);
					break;
				case 16:
					if (!($part = substr($data, $p, 2))) {
						trigger_error($error, E_USER_WARNING);
						return $im;
					}
					$color = unpack('v', $part);
					$color[1] = (($color[1] & 0xf800) >> 8) * 65536 + (($color[1] & 0x07e0) >> 3) * 256 + (($color[1] & 0x001f) << 3);
					break;
				case 8:
					$color = unpack('n', $vide . substr($data, $p, 1));
					$color[1] = $palette[ $color[1] + 1 ];
					break;
				case 4:
					$color = unpack('n', $vide . substr($data, floor($p), 1));
					$color[1] = ($p * 2) % 2 == 0 ? $color[1] >> 4 : $color[1] & 0x0F;
					$color[1] = $palette[ $color[1] + 1 ];
					break;
				case 1:
					$color = unpack('n', $vide . substr($data, floor($p), 1));
					switch (($p * 8) % 8) {
						case 0:
							$color[1] = $color[1] >> 7;
							break;
						case 1:
							$color[1] = ($color[1] & 0x40) >> 6;
							break;
						case 2:
							$color[1] = ($color[1] & 0x20) >> 5;
							break;
						case 3:
							$color[1] = ($color[1] & 0x10) >> 4;
							break;
						case 4:
							$color[1] = ($color[1] & 0x8) >> 3;
							break;
						case 5:
							$color[1] = ($color[1] & 0x4) >> 2;
							break;
						case 6:
							$color[1] = ($color[1] & 0x2) >> 1;
							break;
						case 7:
							$color[1] = ($color[1] & 0x1);
							break;
					}
					$color[1] = $palette[ $color[1] + 1 ];
					break;
				default:
					trigger_error('imagecreatefrombmp: ' . $filename . ' has ' . $meta['bits'] . ' bits and this is not supported!', E_USER_WARNING);
					return false;
			}
			imagesetpixel($im, $x, $y, $color[1]);
			$x++;
			$p += $meta['bytes'];
		}
		$y--;
		$p += $meta['decal'];
	}
	fclose($fh);
	return $im;
}