sinatra-thumbnails

Generate, serve cached thumbnails in Sinatra. Good for simple file-based CMS's.

Minimal example

Consider a small sinatra app that serves a mix of markdown and jpeg content, loosely arranged as follows.

portfolio/
 Gemfile
 app.rb
 views/
    layout.haml
    gallery.haml
 content/
   some_gallery/
     1.jpg           # a pic
     test.jpg        # another pic
     desc.mdown      # a description of some_gallery
   another_gallery/
     yap.jpg         # yet another pic
     desc.mdown      # description of another_gallery

I use bundler, so in my Gemfile

gem 'sinatra-thumbnails', :require => "sinatra/thumbnails"

I have a app.rb like

require 'rubygems'
require 'bundler'
Bundler.require

module ContentHelpers
  def content_path(file)
    File.join("content",params[:gallery], file)
  end
end

helpers do
  include ContentHelpers
end

get "/:gallery" do
  # A gallery has markdown description snippet 
  #
  file =  content_path("desc.mdown")
  if File.exists? file
    @description = Maruku.new(File.read(file)).to_html
  end
  
  # ... and a bunch of jpegs...
  # 
  @images = Dir.glob(content_path("*.{jpg,jpeg,JPG,JPEG}"))
  haml :gallery
end

This is the gallery.haml partial, notice the call to thumbnail_url_for:

#gallery
  #description
    ~ @description
  #images
    - @images.each do |image|
      .asset
        %a{:href => image}
          %img{:src => thumbnail_url_for(image, "200x200")}

That's it.

What it does / why this works

When the browsers loads http://www.myportfolio.com/some_gallery there's the following tag

<img src='public/thumbnails/200x200/content/some_gallery/test.png?original_extension=jpg' />

in the middle of the HTML I get. When a request for that particular URL is comes in, the ImageMagick's convert creates the test.png thumbnail from test.jpg ImageMagick and the directory structure becomes:

portfolio/
  ...
  content/
    ...                  # same as before
  public/
    thumbnails/
      200x200/
        content/
          some_gallery/
            test.png

The next time the very same URL is loaded, and unless test.jpg has changed in the meantime, the test.png is just served and not recreated again.

Contributing to sinatra-thumbnails

Fell free to fork and submit pull requests.