jekyll generator to iterate through image dir and concatenate files under subdirectories including a 'main' subdirectory

gistfile1.rb

module Jekyll
  class ImageListGenerator < Generator
    def generate(site)
      imagemap = {}
      imagearr = []
      dir = ""

      #create a dir and image map
      Dir.glob(File.join(site.source,'_images/**/*')).each {|f| 
          if File.directory?(f) then
              puts File.basename(f)
            if File.basename(f) == 'main' then
                imagemap[dir] = File.basename(f)   
            else
                dir = File.basename(f) 
                imagemap[dir] = nil 
                imagearr = []
            end
          else
            if File.extname(f) == ".jpg" then 
                if imagemap[dir] == 'main' then
                    imagemap[dir] = imagearr.push('main/'+File.basename(f))
                else
                    imagemap[dir] = imagearr.push(File.basename(f))
                end
            end
          end
     }

      #remove keys for nil values
      imagemap.delete_if {|k,v| v.nil?}

      site.config['imagemap'] = imagemap
    end
  end
end