#!/usr/bin/perl

use Image::ExifTool;
use strict;

# I know there is an easier, prettier way to do this, but
# this works for me and I wrote it quickly, so...

my @skip = qw(BlueBalance CreateDate DateTimeOriginal FileName
              FileSize FocalLength35efl ModifyDate RedBalance
              ShutterCount SubSecTime SubSecTimeDigitized
              SubSecTimeOriginal ThumbnailImage ThumbnailLength
              ThumbnailOffset FNumber MaxApertureValue
              ExposureTime ImageSize NEFCurve1 NEFCurve2
              StripByteCounts StripOffsets ImageHeight ImageWidth
              FocalLengthIn35mmFormat PreviewImage
              PreviewImageLength);

my %files = ();
my %exif = ();

foreach my $file (@ARGV) {
  $files{$file} = undef unless -s $file;
    
  my $info = Image::ExifTool->new->ImageInfo($file);

  foreach my $key (sort keys %$info) {
    (my $value = $info->{$key}) =~ s/\s+/ /g;
    push @{$exif{$key}}, $value;
  }

  $files{$file} = $info;
}

my %differences;
my %attributes;

foreach my $file (sort keys %files) {

  my $info = $files{$file};

  foreach my $attribute (sort keys %{$info}) {
    push @{$attributes{$attribute}}, $info->{$attribute};
  }
}

foreach my $attribute (sort keys %attributes) {

    next if grep { $attribute =~ m/$_/ } @skip;

    my @differences = ();
    my $found;

    foreach my $att (@{$attributes{$attribute}}) {
      push @differences, $att;
      foreach my $try (@{$attributes{$attribute}}) {
        $found++ unless $try eq $att;
      }
    }

   @differences = () unless $found;
   $differences{$attribute} = \@differences;
}

my $header = "tag                      ";

foreach my $file (sort keys %files) {
    $header .= sprintf("%-28s  ", $file);
}

print "$header\n";
print '-' x length $header, "\n";

foreach my $diff (sort keys %differences) {

  next unless @{$differences{$diff}};

  printf("%-23s  ", $diff);

  foreach my $value (@{$differences{$diff}}) {
    printf("%-28s  ", $value);
  }
  print "\n";
}