Simple resizer for multiple JPG images based on the 'convert' binary from ImageMagick. Full path to a directory containing JPG files is the first and only command line argument needed. Original files are not overwritten! Resized images are saved in a subfolder.

jpg-resizer.pl

#!/usr/bin/perl -w

use strict;
use warnings;

my $FOLDER_TO_OPEN = $ARGV[0];

opendir (my $directory_handle, $FOLDER_TO_OPEN) or die $!;

my $output_directory_name = "converted-images";
my $output_directory_full_path = $FOLDER_TO_OPEN."/".$output_directory_name;
unless (-e $output_directory_full_path or mkdir $output_directory_full_path) {
	die "Unable to create $output_directory_full_path\n";
}

while (my $file = readdir ($directory_handle)) {
	# Only files are selected:
	next unless (-f "$FOLDER_TO_OPEN/$file");
	# Regular expression is used to find files ending in .jpg:
	next unless ($file =~ m/\.jpg$/);

	my $filepath_to_read = $FOLDER_TO_OPEN."/".$file;
	my $filepath_to_write = $output_directory_full_path."/".$file;

	print "Resizing $file ...\n";
	my $result = `/usr/bin/convert $filepath_to_read -resize 20% $filepath_to_write`;
}

closedir ($directory_handle);

print "Resizing successfully completed!\n";