use strict;
use warnings;

use Imager;

processPics("./images");

sub processPics {
    my $dir = shift;
    my $newDat = '';

    # build list of jpg files to process
    opendir my $dh, $dir or die "Could not open '$dir' for reading '$!'\n";
    my @pics = grep(/\.jpg$/, readdir $dh);
    closedir $dh;

    # check for subdirs and make if missing
    mkdir "${dir}/medium"  unless (-d "${dir}/medium");
    mkdir "${dir}/thumbs"  unless (-d "${dir}/thumbs");
    mkdir "${dir}/upright" unless (-d "${dir}/upright");

    # process image dir
    for my $p (@pics) {
        my $img = Imager->new(file=>"${dir}/${p}", type=>'jpeg')
            or die Imager->errstr();

        my $med   = $img->copy();
        my $thumb = $img->copy();
        my $rot90;

        # sets width to 750px, write out image
        $med = $img->scale(xpixels=>750);
        $med->write(file=>"${dir}/medium/${p}") or die $med->errstr;

        # sets the height to 150px, write out image
        $thumb = $img->scale(ypixels=>150);
        $thumb->write(file=>"${dir}/thumbs/${p}") or die $thumb->errstr;

        # rotate image, write out image
        $rot90 = $img->rotate(degrees=>-90);
        $rot90->write(file=>"${dir}/upright/${p}") or die $rot90->errstr;

        # append filename without the extension
        $newDat .= (split(/\./, $p))[0] . '|';
    }

    # display $newDat after removing trailing |
    chop $newDat if $newDat;
    print "completed: ${newDat}\n";
}


##</code><code>##

use strict;
use warnings;

use Imager;
use MCE;

processPics("./images");

sub processPics {
    my $dir = './images';
    my $newDat = '';

    # build list of jpg files to process
    opendir my $dh, $dir or die "Could not open '$dir' for reading '$!'\n";
    my @pics = grep(/\.jpg$/, readdir $dh);
    closedir $dh;

    # check for subdirs and make if missing
    mkdir "${dir}/medium"  unless (-d "${dir}/medium");
    mkdir "${dir}/thumbs"  unless (-d "${dir}/thumbs");
    mkdir "${dir}/upright" unless (-d "${dir}/upright");

    # construct MCE object
    my $mce = MCE->new(
        max_workers => MCE::Util::get_ncpu(),
        chunk_size  => 1,
        gather      => sub { $newDat .= $_[0]; }, # called inside parent
        user_func   => sub {
            my $p = $_;

            my $img = Imager->new(file=>"${dir}/${p}", type=>'jpeg')
                or die Imager->errstr();

            my $med   = $img->copy();
            my $thumb = $img->copy();
            my $rot90;

            # sets width to 750px, write out image
            $med = $img->scale(xpixels=>750);
            $med->write(file=>"${dir}/medium/${p}") or die $med->errstr;

            # sets the height to 150px, write out image
            $thumb = $img->scale(ypixels=>150);
            $thumb->write(file=>"${dir}/thumbs/${p}") or die $thumb->errstr;

            # rotate image, write out image
            $rot90 = $img->rotate(degrees=>-90);
            $rot90->write(file=>"${dir}/upright/${p}") or die $rot90->errstr;

            # append filename without the extension
            MCE->gather( (split(/\./, $p))[0] . '|' );
        },
    );

    # process image dir in parallel
    $mce->process(\@pics);
    $mce->shutdown();

    # display $newDat line after removing trailing |
    chop $newDat if $newDat;
    print "completed: ${newDat}\n";
}


##</code><code>##

use strict;
use warnings;

use Imager;
use MCE::Child 1.865;
use MCE::Channel;

my $chnl = MCE::Channel->new();

# Create worker pool early in the script.
MCE::Child->create('consumerTask') for 1..MCE::Util::get_ncpu();

# Simulating a persistent web-service.
for (1..1) {
    # process image dir in parallel
    processPics("./images");

    # do something else
    # ...
}

# Signal workers no more work and reap prior to exiting.
$chnl->end(), MCE::Child->waitall();

exit(0);

#==================================
# Producer and Consumer Subroutines
#==================================

sub processPics
{
    my $dir = shift;
    my $newDat = '';

    # build list of jpg files to process
    opendir my $dh, $dir or die "Could not open '$dir' for reading '$!'\n";
    my @pics = grep(/\.jpg$/, readdir $dh);
    closedir $dh;

    # check for subdirs and make if missing
    mkdir "${dir}/medium"  unless (-d "${dir}/medium");
    mkdir "${dir}/thumbs"  unless (-d "${dir}/thumbs");
    mkdir "${dir}/upright" unless (-d "${dir}/upright");

    # send parameters ($dir,$p) to worker pool
    $chnl->send($dir, $_) for (@pics);

    # wait and gather data from workers
    $newDat .= $chnl->recv2() for (1..@pics);

    # display $newDat after removing trailing |
    chop $newDat if $newDat;
    print "completed: ${newDat}\n";
}

sub consumerTask
{
    local $SIG{__DIE__} = sub {
        warn $_[0];
        MCE::Signal::stop_and_exit('TERM');
    };

    while ( my ($dir, $p) = $chnl->recv() ) {
        my $img = Imager->new(file=>"${dir}/${p}", type=>'jpeg')
            or die Imager->errstr();

        my $med   = $img->copy();
        my $thumb = $img->copy();
        my $rot90;

        # sets width to 750px, write out image
        $med = $img->scale(xpixels=>750);
        $med->write(file=>"${dir}/medium/${p}") or die $med->errstr;

        # sets the height to 150px, write out image
        $thumb = $img->scale(ypixels=>150);
        $thumb->write(file=>"${dir}/thumbs/${p}") or die $thumb->errstr;

        # rotate image, write out image
        $rot90 = $img->rotate(degrees=>-90);
        $rot90->write(file=>"${dir}/upright/${p}") or die $rot90->errstr;

        # append filename without the extension
        $chnl->send2( (split(/\./, $p))[0] . '|' );
    }
}