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A set of transformations that can be applied to a blob to create a variant. This class is exposed via the ActiveStorage::Blob::Representable#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.

Methods
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Attributes
[R] transformations
Class Public methods
decode(key)

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

# File activestorage/app/models/active_storage/variation.rb, line 38
def decode(key)
  new ActiveStorage.verifier.verify(key, purpose: :variation)
end
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).

# File activestorage/app/models/active_storage/variation.rb, line 44
def encode(transformations)
  ActiveStorage.verifier.generate(transformations, purpose: :variation)
end
new(transformations)
# File activestorage/app/models/active_storage/variation.rb, line 49
def initialize(transformations)
  @transformations = transformations
end
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 ::decode. Otherwise, it is assumed to be a transformations Hash and is passed directly to the constructor.

# File activestorage/app/models/active_storage/variation.rb, line 26
def wrap(variator)
  case variator
  when self
    variator
  when String
    decode variator
  else
    new variator
  end
end
Instance Public methods
key()

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

# File activestorage/app/models/active_storage/variation.rb, line 72
def key
  self.class.encode(transformations)
end
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.

# File activestorage/app/models/active_storage/variation.rb, line 55
def transform(image)
  ActiveSupport::Notifications.instrument("transform.active_storage") do
    transformations.each do |name, argument_or_subtransformations|
      image.mogrify do |command|
        if name.to_s == "combine_options"
          argument_or_subtransformations.each do |subtransformation_name, subtransformation_argument|
            pass_transform_argument(command, subtransformation_name, subtransformation_argument)
          end
        else
          pass_transform_argument(command, name, argument_or_subtransformations)
        end
      end
    end
  end
end