Rename images following their proper creation date

rename-by-metadata.rb

#!/usr/bin/env ruby

require 'date'
require 'fileutils'

require 'exif' # brew install libexif; gem install exif

Dir['*.{JPG,jpg}'].each do |source|
  time =
    begin
      t = Exif::Data.new(File.open(source)).date_time_original

      raise Exif::NotReadable if t.nil? || t < '2000'

      t.sub(':', '-').sub(':', '-')
    rescue Exif::NotReadable
      # fallback to modified date, if exif data is not available or unrealistic
      File.mtime(source).to_s.sub(/ \+0\d00/, '')
    end

  target = time.gsub(':', '_') + '.jpg'

  next if target == source

  raise "File exists: #{target}" if File.exists?(target)
  FileUtils.mv(source, target)
end