Once you get the dimentions using Image::Magick or whatever, here's code to maintain proportions:

sub scale_dimentions {
   my ($width, $height, $max_width, $max_height) = @_;

   my $width_factor;
   my $height_factor;
   my $new_width;
   my $new_height;
   my $factor;

   $width_factor  = $max_width  / $width;
   $height_factor = $max_height / $height;

   if ($width_factor < 1 || $height_factor < 1)
   {
      if ($width_factor < $height_factor) {
         $factor = $width_factor;
      } else {
         $factor = $height_factor;
      }

      $new_width  = int($width  * $factor + 0.5);
      $new_height = int($height * $factor + 0.5);
   } else {
      $new_width  = $width;
      $new_height = $height;
   }

   return ($new_width, $new_height);
}

printf("%d,%d$/", scale_dimentions(2272, 1704, 800, 600));  # 800,600
printf("%d,%d$/", scale_dimentions(1704, 2272, 800, 600));  # 450,600
printf("%d,%d$/", scale_dimentions(2272, 1704, 150, 150));  # 150,112
printf("%d,%d$/", scale_dimentions(1704, 2272, 150, 150));  # 112,150
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