#! /usr/bin/zsh

for img in *.jpg; do
  if [[ -f "thumbs/JPEG/${img%.jpg}.jpg" ]]; then
#    echo "Thumbnail $img exists."
  else
    echo "Thumbnail $img does not exist."
    convert "$img" -thumbnail 75x -auto-orient "thumbs/JPEG/${img%.jpg}.jpg"
  fi
done