#! /usr/bin/perl -w

use strict;
use Image::Info;
use Time::Local;
use vars qw ($indir);

my $indir = shift;
die "specifiy input directory" unless (defined $indir);
my %pics;

unless (opendir(DIR,$indir)) {
	die "Could not open directory $indir: $!";
}
while (my $file = readdir(DIR)) {
	next unless ($file =~ /\.jpg$/i);
	my ($date,$time) = split(/ /, exifInfo("$file"));
	my ($year,$month,$mday) = split(/\:/,$date);
	my ($hour,$min,$sec) = split(/\:/,$time);
	my $stamp = timelocal($sec,$min,$hour,$mday,$month-1,$year);
	$pics{$file} = $stamp;
}

my @sorted = sort { $pics{$a} <=> $pics{$b} } keys %pics;
for (my $i = 0; $i <= $#sorted; $i++) {
	my $filename = $sorted[$i];
	my $stamp = $pics{$filename};
	my $newfilename = sprintf("%03d_$filename",$i+1);
	print "$filename --> $newfilename ($stamp)\n";
	rename "$indir/$filename", "$indir/$newfilename";
}

exit;

sub exifInfo {
	my $infile = shift;
	my $exif = Image::Info::image_info("$indir/$infile");

	my $stamp = $exif->{DateTimeOriginal};
	$stamp = "" unless (defined $stamp);

	return $stamp;  
}