How to make thumbnails of your images using a Perl script

You can use ImageMagick. It is a wrapper for a very good image handling module, with the product home page at: http://www.imagemagick.org/. We strongly suggest you read all the documentation on their page, and take your time at installing it.

On the ImageMagick product page you will find a link to instructions of how to install Perl::Magick, the interface to any script that will use this application: http://www.imagemagick.org/www/perl.html

Here is an example subroutine that will help you build your code into the shop, or adapt it to any other script you want:

sub _MakeThumbnails {
  use Image::Magick;
  my ($x, @FullImages);
  my $ProductDir = shift || "/var/www/html/images/shops/city/products";
# you can use percents
  my $Ratio      = shift || ''; # you can pass a percentage like: 50%
# or you can use the following limits format
  my $MaxHeight  = shift || ''; # a number in pixels, i.e.: 100
  my $MaxWidth   = shift || '';
  die 'Provide some parameter to define thumbnail sizes' 
    if ! $Ratio && ! ($MaxHeight && $MaxWidth);
  
# We read all the files in that directory and we select 
# all the images that are not already thumbnails. Feel free to 
# customize the search here to match your thumbnail naming convention.
# ...you DO have a naming convention, right? :)
  opendir(THISDIR, $ProductDir);
  my @Items = grep(!/^\.\.?$/,readdir(THISDIR));
  foreach $x(@Items) {push(@FullImages, $x) if $x !~ /_thmb\.\w+$/oi}
  closedir(THISDIR);
  my $p = new Image::Magick;
  
  foreach $x(@FullImages) {
    next if $x !~ /^(.*)(\..+)$/;
    my $Target = $ProductDir.'/'.$1.'_thmb'.$2;
    $p->Read("$ProductDir/$x");
    my ($w, $h) = $p->Get('width', 'height');
    $h = 1 if ! $h;
    $w = 1 if ! $w;
    if ($MaxHeight || $MaxWidth) {
      my $HR = $MaxHeight / $h;
      my $WR = $MaxWidth / $w;
      $Ratio = $HR && $HR < $WR ? $HR : $WR;
    }
    $w = $Ratio =~ /\s*(.*)\s*\%/o ? int($w * $1 / 100) : int $w * $Ratio;
    $h = $Ratio =~ /\s*(.*)\s*\%/o ? int($h * $1 / 100) : int $h * $Ratio;
    $p->Resize(
      width => $w,
      height => $h,
    );
    $p->Write($Target);
  }
}