Class to generate thumbnails for images in a dir stored in an Amazon S3 bucket.

generate_thumbnail.rb

#!/usr/bin/env ruby

###################################################
#
# Class to generate thumbnails for images in a dir
# stored in an Amazon S3 bucket.
#
# simon@newtriks.com - 10/2012
#
###################################################

require 'image_sorcery' # Required for image conversion, needs ImageMagick installed
require 'aws/s3' # Required to interact with Amazon S3
require 'fileutils' # Required for creating temp dir
require 'tmpdir' # Required for tempdir logic

class GenerateThumbnail

  # TODO: Error catching
	# TODO: Only convert if an image
	def initialize(u_p, b)
		connect_to_S3({ key: 'AWS-KEY-GOES-HERE', 
						secret: 'AWS-SECRET-GOES-HERE', 
						region: 's3-eu-west-1.amazonaws.com'})
		generate({ upload_path: u_p, 
				   bucket: b})
	end

	private

		# Expects a key/secret, plus region which was added 
		# due to EU region issue: https://github.com/marcel/aws-s3/issues/4
		def connect_to_S3(options={})
			puts "Connection to amazon #{options.values}"
			AWS::S3::DEFAULT_HOST.replace options[:region]
			AWS::S3::Base.establish_connection!(:access_key_id => options[:key], :secret_access_key => options[:secret])
		end

		# Expects and upload path and a bucket.
		# 1. Creates a temp dir
		# 2. Gets the contents of specified dir in bucket
		# 3. Loops thorough each file (image) in dir & creates a thumbnail
		def generate(options={})
			@tmp_path = Dir.mktmpdir
			Dir.mkdir "#{@tmp_path}/t" 
			filenames = AWS::S3::Bucket.find(options[:bucket], :prefix => options[:upload_path])
			filenames.each do |fname|
				filename = fname.key.scan(/[\w_.-]*?(?=\?)|[\w_.-]*$/)[0]
				if filename.length > 1
					puts "Convert file: #{filename}"
					open("#{@tmp_path}/#{filename}", 'w') do |file|
						AWS::S3::S3Object.stream("#{fname.key}", options[:bucket]) do |chunk|
					 	 	file.write chunk
						end
					end
					image = Sorcery.new("#{@tmp_path}/#{filename}")
					image.convert("#{@tmp_path}/t/thumbnail_#{filename}", :thumbnail => "128x96")
				end
			end
			uploadFilesToBucket({ path: @tmp_path, 
				   				  upload_path: options[:upload_path], 
				   			      bucket: options[:bucket]})
			FileUtils.remove_entry_secure @tmp_path
		end

		# Expects a dir with thumbs, upload path and bucket
		# 1. Gets all the files from the temp dir
		# 2. Loops through the files and uploads to specified dir in bucket.
		def uploadFilesToBucket(options={})
			puts "Upload files to Amazon S3 bucket: #{options[:bucket]}."
			filenames = Dir.entries("#{@tmp_path}/t/").select { |file| /.jpg|.pdf|.png|.JPG|.PNG/ =~ file }
			filenames.each do |name|
			  puts "Uploading #{@tmp_path}/t/#{name} to #{options[:upload_path]}/#{name}"
			  AWS::S3::S3Object.store("#{options[:upload_path]}/#{name}",open("#{@tmp_path}/t/#{name}").read,options[:bucket],:access => :public_read)
			end
		end
end

# Generate thumbnail for images in a directory
GenerateThumbnail.new("my_path/to/a/directory", "my-bucket")

# END