Callisto

A library that generates thumbnails on the fly. Requires the ImageMagick command line utility to be installed.

Add this line to your application's Gemfile:

gem 'callisto'

And then execute:

$ bundle

Or install it yourself as:

$ gem install callisto

A thumbnail may be generated as follows:

options = {
  :root_path        => Rails.root,
  :prefix           => "public/images/cache",
  :public_path      => "/images/cache",
  :fixed_size       => "140x90"
}
thumbnail = Callisto::Thumbnail.new(options)
thumbnail.save # Returns the file name using the `public_path` value

The image name generated is based on the parameters used. However, the root_path will always be ignored, in order to allow the application path to be changed without having to regenerate the thumbnails (eg. this always happens after a capistrano deploy).

The fixed_size option will scale the image then crop it to fit the specified dimension. You may also resize the photo without cropping it by using either the min_size or max_size options. min_size will scale down the photo while ensuring that neither the width or height is less than the specified value, whereas max_size does the opposite.

You may also set defaults or set additional options by using a configure block:

Callisto.configure do |config|
  config.thumbnail_root_path   = Rails.root
  config.thumbnail_prefix      = "public/images/cache"
  config.bin_path              = "/usr/local/bin"
  config.max_workers           = 4
end

1. Fork it
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Added some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create new Pull Request