This Gem helps you create any kind of thumbnails on-the-fly.

• define your various thumb-formats inside of your model and let smartthumbs do the rest.
• writes created thumbs to the public directory - every thumb is only created once and only if needed
• Works with blob-based records and filename-based records
• can be implemented in several models
• define which strategy should be used to resize your images

Add the Gem to your Gemfile:

gem "smartthumbs"

and run

bundle install

Afterwards you should create an initializer-script in config/initializers:

Smartthumbs::Config.run do |config|
  config[:valid_classes] = ["Image"]
  
  config[:assume_klass] = "Image" # optional
end

Smartthumbs needs to know all classes that you want to use smartthumbs with. Pass them as an array of strings via :valid_classes .

By default smartthumbs generates urls like "/th/klass-name/format/record-id.extension". If you only have a single class, you can set the default-class and prevent this class name from appearing in that url.

That's it, you're ready to use smartthumbs.

class Image < ActiveRecord::Base
	smartthumbs :file => :file_path, :extension => "jpg", :formats => {
	  "thumb" => ["800x200", :cut, :w],
		"small" => ["100x100", :fit],
		"tiny" => ["15x15", :fill]
	}

  def file_path
    "#{Rails.root}/tmp/uploads/#{self.id}.jpg"
  end
end  



class Image < ActiveRecord::Base  
  smartthumbs :blob => :db_blob_column, :extension => :my_extension, :formats => {
   "thumb" => ["800x100", :fit, :e]
  }

  def my_extension
    "jpg"
  end
end

Since version 0.0.4 it's possible to pass a lambda function as :formats. That makes it possible to store the formats inside of a model:

class ThumbFormat < ActiveRecord::Base
  def config
  	["#{width}x#{height}", method.to_sym, orientation.try(:to_sym)]
  end
end

class Image < ActiveRecord::Base
  smartthumbs :file => :file, :extension => "jpg", :formats => lambda{|format|
    ThumbFormat.find_by_name(format).try(:config)
  }
end

<%= thumb_tag, @image, "tiny", :class => "red-border" %>

will generate something like:

<img src="/th/my_image/tiny/5.jpg" class="red-border"/>

Copyright (c) 2011 Alexander Pauly, released under the MIT license