exifpic.pl

# /usr/bin/perl -w
use 5.010;
use strict;
use warnings;
use threads;
use Thread::Queue;
use autodie qw(:all);
use Image::ExifTool qw(ImageInfo);
use Data::Dumper;
use Imager;
use File::Slurp qw(read_file);

# Imager needs to be preloaded if we're using threads.
Imager->preload;

# Set up our work queue. Right now it's just @ARGV.

my $work_queue = Thread::Queue->new;
$work_queue->enqueue(@ARGV);
$work_queue->end;

# Spawn our threads, each of which will process files until we're done.

my @threads;
my $cores = get_cores();

for (1..$cores) {
    push(@threads,
        threads->create( sub {
            while (my $src = $work_queue->dequeue) {
                process_image($src);
            }
        })
    );
}

# Join threads.
foreach my $thread (@threads) { $thread->join; }

sub process_image {
    my ($raw) = @_;

    my ($new) = $raw =~ m{(.*).CR2$}i;

    next if not $new;   # Skip non-CR2 files
    $new .= ".jpg";

    say "$raw -> $new...";

    my $exif = ImageInfo($raw, [qw(PreviewImage Orientation)], { Binary => 1 });

    my ($rotation) = ( $exif->{Orientation} =~ /(\d+)/ );

    my $img = Imager->new();
    $img->read(data => ${$exif->{PreviewImage}})
        or die $img->errstr;

    $img
        ->scale(type=>'min', xpixels=>2048, ypixels=>2048)
        ->rotate(degrees => $rotation)
        ->write(file=>$new, type=>'jpeg')
    ;

    return;
}

sub get_cores {
    my $cpuinfo = read_file("/proc/cpuinfo");

    my $max_threads;

    # Walk through all the cores to figure out how many we have.
    while ($cpuinfo =~ m{^processor\s*:\s*(?<cores>\d+)}msgi ) { 
        $max_threads = $+{cores}+1;
    };

    return $max_threads;

}

To use:

exifpic.pl *.CR2