Rename files inside the ~/Desktop/Screenshots folder to something slightly more sane.

rename-sshots.rb

#!/usr/bin/env ruby

# Rename files inside the ~/Desktop/Screenshots folder to something
# slightly more sane. Called via a folder action, but does not
# use any parameters from the action (the script scans for the files.)
#
# Example original filenames:
#  ScreenCapture 2011-01-03 at 8.06.39 AM.png
#  ScreenCapture 2011-01-03 at 8.06.39 AM (2).png
# Example destination filenames:
#  screencap_2011-01-03_08-06-39.png
#  screencap_2011-01-03_08-06-39_2.png
#
# Note this script only works with my customizations to the defaults
# com.apple.screencapture name (ScreenCapture) and
# com.apple.screencapture location (~/Desktop/Screenshots).
# Adjust as necessary.

require 'pp'

SCREENSHOT_FOLDER = '/Users/BinaryMuse/Desktop/Screenshots'
# http://rubular.com/r/0mtUw9fq6s
SCREENCAP_REGEX = /ScreenCapture (\d*)-(\d*)-(\d*) at (\d*)\.(\d*)\.(\d*) ([A-Z]{2})( \(([^\.\)]*)\))?\.(.*)/i

# Convert an hour and a meridian to a 24-hour time.
def mil_hour(hour, meridian)
  hour = hour.to_i
  # Special cases at noon and midnight. All other times += 12 during PM.
  if hour == 12
    hour = 0 if meridian == "AM"
  else
    hour += 12 if meridian == "PM"
  end
  "%02d" % hour
end

Dir["#{SCREENSHOT_FOLDER}/*"].each do |file|
  basename = File.basename(file)
  matches = basename.scan(SCREENCAP_REGEX).flatten
  next if matches.empty?

  # Convert matches to hash for easier reference
  parts = {}
  [:year, :month, :day, :hour, :minute, :second, :meridian, :_, :suffix, :extension].each_with_index do |sym, i|
    parts[sym] = matches[i]
  end

  # date part
  new_name =  "screencap_#{parts[:year]}-#{parts[:month]}-#{parts[:day]}_"
  # time part
  new_name += "#{mil_hour(parts[:hour], parts[:meridian])}-#{parts[:minute]}-#{parts[:second]}"
  # suffix, if any
  new_name += "_#{parts[:suffix]}" unless parts[:suffix].nil?
  # extension
  new_name += ".#{parts[:extension]}"

  File.rename(file, "#{SCREENSHOT_FOLDER}/#{new_name}")
end