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_to_limit: [100, 100], colourspace: "b-w", rotate: "-90", saver: { trim: true })

The options map directly to ImageProcessing commands.

Methods

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 33
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 39
def encode(transformations)
  ActiveStorage.verifier.generate(transformations, purpose: :variation)
end

new(transformations)

# File activestorage/app/models/active_storage/variation.rb, line 44
def initialize(transformations)
  @transformations = transformations.deep_symbolize_keys
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 ActiveStorage::Variation.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 21
def wrap(variator)
  case variator
  when self
    variator
  when String
    decode variator
  else
    new variator
  end
end

Instance Public methods

content_type()

# File activestorage/app/models/active_storage/variation.rb, line 68
def content_type
  MiniMime.lookup_by_extension(format.to_s).content_type
end

default_to(defaults)

# File activestorage/app/models/active_storage/variation.rb, line 48
def default_to(defaults)
  self.class.new transformations.reverse_merge(defaults)
end

digest()

# File activestorage/app/models/active_storage/variation.rb, line 77
def digest
  OpenSSL::Digest::SHA1.base64digest Marshal.dump(transformations)
end

format()

# File activestorage/app/models/active_storage/variation.rb, line 60
def format
  transformations.fetch(:format, :png).tap do |format|
    if MiniMime.lookup_by_extension(format.to_s).nil?
      raise ArgumentError, "Invalid variant format (#{format.inspect})"
    end
  end
end

key()

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

# File activestorage/app/models/active_storage/variation.rb, line 73
def key
  self.class.encode(transformations)
end

transform(file, &block)

Accepts a File object, performs the transformations against it, and saves the transformed image into a temporary file.

# File activestorage/app/models/active_storage/variation.rb, line 54
def transform(file, &block)
  ActiveSupport::Notifications.instrument("transform.active_storage") do
    transformer.transform(file, format: format, &block)
  end
end