This code iterates through every .html file contained in a given folder and, for each template found, it looks for every image (<img>) contained (with Nokogiri gem) in the document. Then it dynamically calculates the image size (with fastimage gem) adding the “height” and “width” attributes. Finally it saves the template. Colorize gem is only us…

rakefile.rb

# Tested on Ruby v.1.9.3 - Author: Fabrizio Calderan, 3.14.2013
#
# Install these gems with
#    $> sudo gem install fastimage nokogiri colorize
#
# Then copy this source into a file named “rakefile” and run with
#    $> rake
#
require "fastimage"
require "nokogiri"
require "colorize"

task :default do

  glob_replace = 0
  file_replace = 0

  # for each .html template in the folder...
  Dir.glob("*.html") do |tpl|

    puts "=> #{tpl.yellow}"

    # read file content...
    html = File.open(tpl, "r").read

    # create a DOM structure...
    document = Nokogiri::HTML(html);

    # for each <img> contained in the structure
    document.css('img').map{ |image|

      # ...find the 'src' attribute...
      url = image['src']

      # ...and if the image exists in the given url
      if File.exist?(url)
      
        # ...compute width and height...
        size = FastImage.size(url)
        puts "\t#{url} (width: #{size[0]}px, height: #{size[1]}px)"
        
        # ...and add width & height attributes
        image['width'] = size[0]
        image['height'] = size[1]
        file_replace += 1
      end
    }

    # then overwrite the template with update document
    File.open(tpl, 'w') { |f|
      f.write(document)
      puts "\n\tSuccessfully updated #{tpl} - #{file_replace} replacements\n".green
      glob_replace += file_replace
      file_replace = 0
    }

  end

  puts "\n\tTotal replacements done: #{glob_replace}".green

end