ruby script for generating contact sheet images for video files.

vidsnaps.rb

# ruby script for generating contact sheet images for video files.  
# can be configured via an ini file which is expected to be in the current working directory.
# Requirements:
# - VLC (http://videolan.org) must be installed and available in the system PATH.  
# - gem iniparse.  
#
# vidsnaps will open the given video in VLC and save a screenshot at predetermined time intervals.  
# By default it will save 20 images 500 seconds apart starting at the very beginning of the video.  
# If these settings take it beyond the end of the video, a number of black screens will be generated, which can be ignored/deleted
# images are saved as png files using the format "##h##m##s.png".  
#
# On Windows this script works well compiled into an ocra EXE (https://github.com/larsch/ocra).  Videos can then just be dragged right onto the EXE icon to produce the screens.
#
# example ini file:
# [Defaults]
# outputFolder=.	; output to current directory
# timeOffset=10		; first image 10 seconds in
# imageCount=20		; produce 20 images
# imageSpacing=500	; each image 500 seconds appart
# inputFile=test.avi
# outputFormat=png

require 'iniparse'
ininame = 'vidsnaps.ini'

outputFolder = "."
timeOffset = 0.0
imageCount = 1
imageSpacing = 0.5
runTime = 2
useOutputPrefix = false
outputFormat = "png"
if File.exists?(ininame)
	iniDoc = IniParse.parse(File.read(ininame)) # => IniParse::Document
	if !iniDoc['Defaults']['outputFolder'].nil?
		outputFolder = iniDoc['Defaults']['outputFolder']
	end
	if !iniDoc['Defaults']['timeOffset'].nil?
		timeOffset = iniDoc['Defaults']['timeOffset'].to_f
	end
	if !iniDoc['Defaults']['runTime'].nil?
		runTime = iniDoc['Defaults']['runTime'].to_f
	end
	if !iniDoc['Defaults']['imageCount'].nil?
		imageCount = iniDoc['Defaults']['imageCount'].to_i
	end
	if !iniDoc['Defaults']['imageSpacing'].nil?
		imageSpacing = iniDoc['Defaults']['imageSpacing'].to_f
	end
	if !iniDoc['Defaults']['outputFormat'].nil?
		outputFormat = iniDoc['Defaults']['outputFormat']
	end
	if !iniDoc['Defaults']['inputFile'].nil?
		inputFile = iniDoc['Defaults']['inputFile']
	end
	if !iniDoc['Defaults']['prefixOutputWithInput'].nil?
		useOutputPrefix = iniDoc['Defaults']['prefixOutputWithInput']
	end
end

if inputFile.nil? && ARGV.count < 1
	puts "First argument must be video filename"
	exit 1
end
if ARGV.count == 1
	inputFile = ARGV[0]
end

puts "generating screens for #{inputFile}"
puts "with parameters: "
puts "  outputFolder #{outputFolder}"
puts "  timeOffset #{timeOffset}" 
puts "  imageCount #{imageCount}" 
puts "  imageSpacing #{imageSpacing}" 
puts "  runTime #{runTime}" 
puts "  useOutputPrefix #{useOutputPrefix}" 
puts "  outputFormat #{outputFormat}" 
puts "  inputFile #{inputFile}" 

for i in 1..imageCount
	startTime = i*imageSpacing+timeOffset
	hours = (startTime / 60 / 60).to_i
	minutes = (startTime / 60 - hours*60).to_i
	seconds = startTime - minutes*60.0 - hours*3600.0

	puts "snapshot at #{"%02d" % hours}:#{"%02d" % minutes}:#{"%02f" % seconds}..."

	if useOutputPrefix
		filePrefix = "#{inputFile.chomp(File.extname(inputFile))}_"
	else
		filePrefix = ""
	end
	imagePrefix = "#{filePrefix}#{"%02d" % hours}:#{"%02d" % minutes}:#{"%02.3f" % seconds}"

	command = "vlc \"#{inputFile}\" --verbose=0 --quiet-synchro --start-time=#{startTime} --run-time=#{runTime} --scene-format=#{outputFormat} --aout=dummy --video-filter=scene --vout=dummy --scene-path=. --scene-replace --scene-prefix=#{imagePrefix} -Idummy -q vlc://quit"
	puts command
	system(command)
	puts "done."
end
puts "done."