Custom renderer for redcarpet to render paperclip - images by their id and additional css

paperclip_renderer.rb

# quick'm'dirty way to allow paperclip image-ids
# instead of urls be passed to Redcarpet
# so you can do: 
# ![title](42 'thumb|pull-right') - whereas 'thumb' is your available paperclip-style and 'pull-right' a css-class
# and also the knwon way:
# ![title](http://i.ytimg.com/vi/Z6po6SS9Uz4/maxresdefault.jpg "my alt text")
# all this b'cause there is no 'super' in redcarpet...
#
class PaperclipRender < Redcarpet::Render::HTML
  include ActionView::Helpers::AssetTagHelper
    
  # my image-object here  has_attached_file: :data
  # we overwrite Redcarpet::Render::HTML#image
  #
  def image(link_or_id, style_and_css_or_alt, title)  
    if link_or_id.to_i > 0
      args = style_and_css_or_alt.split("|")
      style = args[0].to_sym
      css = args[1] 
      # .find_by here b'cause it won't raise ActiveRecord::RecordNotFound
      # if none found - no image output
      if img = Image.find_by(id: link_or_id)
        image_tag(img.data.url(style), title: title, alt: img.title, class: css)
      else
        ''
      end
    else
      # just do it like Redcarpet::Render::HTML would do
      # so we can still use default image markdown
      image_tag(link_or_id, title: title, alt: style_and_css_or_alt)
    end
  end
end

# then make use of it in your helper:
def markdown(content)
  md = ::Redcarpet::Markdown.new(
                            PaperclipRender, # instead of Redcarpet::Render::HTML
                            space_after_headers: true, 
                            tables: true, 
                            quote: true,
                            hard_wrap: true
                           ) 
  md.render(content).html_safe if content
end