Bash script used in ifeelmaps.com to compare image sizes

compare-imgs.sh

#!/bin/bash

# Compare every file passed over stdin with it's converted one
#   i.e. file.extension vs file_imagemagick_converted.extension and echo the bigger one of each pair
#
# Usage:
#   ./compare-imgs.sh < converted_images > bigger_imgs
#
# Arguments:
#   stdin - list of filenames

suffix=imagemagick_converted # the suffix used to generate converted images

while read -r filename; # loop over filenames passed over stdin
do
  dot_index=`expr index $filename .` # find the dot index in filename
  name=${filename:0:dot_index-1}     # characters before the dot
  extension=${filename:dot_index}    # characters after the dot

  converted="$name"_"$suffix".$extension

  if [ -e "$converted" ] # converted image exists?
  then
    size_original=`stat -c%s $filename`
    size_converted=`stat -c%s $converted`

    if [[ $size_original -gt $size_converted ]]; then
      echo $filename # original is bigger
    else
      echo $converted # converted is bigger
    fi
  fi
done