A set of transformations that can be applied to a blob to create a variant. This class is exposed via the ActiveStorage::Blob#variant method and should rarely be used directly.

In case you do need to use this directly, it's instantiated using a hash of transformations where the key is the command and the value is the arguments. Example:

ActiveStorage::Variation.new(resize: "100x100", monochrome: true, trim: true, rotate: "-90")

You can also combine multiple transformations in one step, e.g. for center-weighted cropping:

ActiveStorage::Variation.new(combine_options: {
  resize: "100x100^",
  gravity: "center",
  crop: "100x100+0+0",
})

A list of all possible transformations is available at www.imagemagick.org/script/mogrify.php.

Namespace

Class

Methods

Attributes

[R] transformations

Class Public methods

decode(key)

Returns a Variation instance with the transformations that were encoded by encode.

📝 Source code 
# File activestorage/app/models/active_storage/variation.rb, line 42
    def decode(key)
      new ActiveStorage.verifier.verify(key, purpose: :variation)
    end
🔎 See on GitHub

encode(transformations)

Returns a signed key for the transformations, which can be used to refer to a specific variation in a URL or combined key (like ActiveStorage::Variant#key).

📝 Source code 
# File activestorage/app/models/active_storage/variation.rb, line 48
    def encode(transformations)
      ActiveStorage.verifier.generate(transformations, purpose: :variation)
    end
🔎 See on GitHub

new(transformations)

📝 Source code 
# File activestorage/app/models/active_storage/variation.rb, line 53
  def initialize(transformations)
    @transformations = transformations
  end
🔎 See on GitHub

wrap(variator)

Returns a Variation instance based on the given variator. If the variator is a Variation, it is returned unmodified. If it is a String, it is passed to ActiveStorage::Variation.decode. Otherwise, it is assumed to be a transformations Hash and is passed directly to the constructor.

📝 Source code 
# File activestorage/app/models/active_storage/variation.rb, line 30
    def wrap(variator)
      case variator
      when self
        variator
      when String
        decode variator
      else
        new variator
      end
    end
🔎 See on GitHub

Instance Public methods

key()

Returns a signed key for all the transformations that this variation was instantiated with.

📝 Source code 
# File activestorage/app/models/active_storage/variation.rb, line 79
  def key
    self.class.encode(transformations)
  end
🔎 See on GitHub

transform(image)

Accepts an open MiniMagick image instance, like what's returned by MiniMagick::Image.read(io), and performs the transformations against it. The transformed image instance is then returned.

📝 Source code 
# File activestorage/app/models/active_storage/variation.rb, line 59
  def transform(image)
    ActiveSupport::Notifications.instrument("transform.active_storage") do
      transformations.each do |name, argument_or_subtransformations|
        validate_transformation(name, argument_or_subtransformations)
        image.mogrify do |command|
          if name.to_s == "combine_options"
            argument_or_subtransformations.each do |subtransformation_name, subtransformation_argument|
              validate_transformation(subtransformation_name, subtransformation_argument)
              pass_transform_argument(command, subtransformation_name, subtransformation_argument)
            end
          else
            validate_transformation(name, argument_or_subtransformations)
            pass_transform_argument(command, name, argument_or_subtransformations)
          end
        end
      end
    end
  end
🔎 See on GitHub