Thumbs on the Fly - LipsiaADMIN

When our staff build the frontend of a site is always necessary redefine the thumbs of an Image.

99% of our customers change the size or the final layout is a little different

It's true our attachment table can define thumbs and we can reprocess them like showed in this article

But if don't want every time add a new line in our code and reprocess all of them?

If the image did't reside on our server?

image_tag("/path/to/my/image.png", :size => "180#")

image_tag("http://www.remote.com/image.png", :size => "180x180!")

Create on the fly (and once time) a new image in our public folder

For all this reasons I create a small but usefull helper

The code is pretty documented

require 'open-uri'
def image_tag(source, options = {})
  options.symbolize_keys!
  # We set here the upload path
  upload_path = "uploads/thumbs"
  # Now we can create a thumb on the fly
  if options[:size] || options[:width] || options[:height]
    begin
      geometry   = options[:size]
      geometry ||= [options[:width], options[:height]].join("x")
      filename   = File.basename(source)
      # Checking if we have just process them 
      # We don't want to do the same job two times
      if File.exist?("#{Rails.root}/public/#{upload_path}/#{geometry}_#{filename}")
        options[:src] = "/#{upload_path}/#{geometry}_#{filename}"
      else # We need to create the thumb
        FileUtils.mkdir("#{Rails.root}/tmp") unless File.exist?("#{Rails.root}/tmp")
        # We create a temp file of the original file
        # Notice that we can download them from an url! 
        # So this Image can reside anywhere on the web
        if source =~ /#{URI.regexp}/
          tmp = File.new("#{Rails.root}/tmp/#{filename}", "w")
          tmp.write open(source).read
          tmp.close
        else # If the image is local
          tmp = File.open(File.join("#{Rails.root}/public", 
                          path_to_image(source).gsub(/\?+\d*/, "")))
        end
        # Now we generate a thumb with our Thumbnail Processor (based on Paperclip)
        thumb = Lipsiadmin::Attachment::Thumbnail.new(tmp, 
                                                      :geometry => geometry).make
        # We check if our dir exists
        unless File.exist?("#{Rails.root}/public/#{upload_path}")
          FileUtils.mkdir("#{Rails.root}/public/#{upload_path}")
        end
        # Now we put the image in our public path
        new_file_path = "#{Rails.root}/public/#{upload_path}/#{geometry}_#{filename}"
        File.open(new_file_path, "w") do |f|
          f.write thumb.read
        end
        # Finally we return the new image path
        options[:src] = "/#{upload_path}/#{geometry}_#{filename}"
      end
    rescue Exception => e
      options[:src] = path_to_image(source)
    ensure
      File.delete(tmp.path)   if tmp   && source =~ /#{URI.regexp}/
      File.delete(thumb.path) if thumb
    end
  end
  options[:src] ||= path_to_image(source)
  options[:alt] ||= File.basename(options[:src], '.*').
                    split('.').first.to_s.capitalize

  if mouseover = options.delete(:mouseover)
    options[:onmouseover] = "this.src='#{image_path(mouseover)}'"
    options[:onmouseout]  = "this.src='#{image_path(options[:src])}'"
  end

  tag("img", options)
end