use strict;

my $debug=0;

sub readUInt8
	{
	my ($fh) = @_;
	my $data;

	read($fh, $data, 1);

	return unpack("C", $data);
	}


sub readUInt16
	{
	my ($fh) = @_;
	my $data;

	read($fh, $data, 2);

	return unpack("n16", $data);
	}


sub skipBytes
	{
	my ($fh, $len) = @_;
	my $data;

	printf("  Skipping %d bytes\n", $len) if ($debug);
	read($fh, $data, $len);
	}


sub skipSection
	{
	my ($fh, $v) = @_;
	my $len = readUInt16($fh);

	skipBytes($fh, $len-2);
	}


sub getImageInfo
	{
	my ($filename) = @_;
	my $v;
	my $fh;
	my $width=0;
	my $height=0;
	my $type="";

	open($fh, $filename);
	binmode($fh);

	$v = readUInt16($fh);

	if ($v == 0xffd8)
		{
		my $done=0;

		while (!$done)
			{
			$v = readUInt16($fh);
			printf("Section %x\n", $v) if ($debug);
			if ($v == 0xffe0
				|| $v == 0xffdb
				|| $v == 0xffe0
				|| $v == 0xffe1
				|| $v == 0xffe2
				|| $v == 0xffe3
				|| $v == 0xffe4
				|| $v == 0xffe5
				|| $v == 0xffe6
				|| $v == 0xffe7
				|| $v == 0xffe8
				|| $v == 0xffe9
				|| $v == 0xffea
				|| $v == 0xffeb
				|| $v == 0xffec
				|| $v == 0xffed
				|| $v == 0xffee
				|| $v == 0xffc4
				|| $v == 0xffe0
				|| $v == 0xfffe
				)
				{
				skipSection($fh, $v);
				}
			elsif ($v == 0xffdd)
				{
				skipBytes($fh, 4);
				}
			elsif ($v == 0xffc0)
				{
				$v = readUInt16($fh);	# len
				$v = readUInt8($fh);	# precision
				$height = readUInt16($fh);	# width
				$width = readUInt16($fh);	# height
				$type = "jpg";
				last;
				}
			else
				{
				printf("$filename - Unexpected value %x\n", $v);
				last;
				}
			}
		}

	close($fh);

	return ($type, $width, $height);
	}