Active Storage Variation

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.

πŸ“ Source code 
# File activestorage/app/models/active_storage/variation.rb, line 35
    def decode(key)
      new ActiveStorage.verifier.verify(key, purpose: :variation)
    end
πŸ”Ž 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).

πŸ“ Source code 
# File activestorage/app/models/active_storage/variation.rb, line 41
    def encode(transformations)
      ActiveStorage.verifier.generate(transformations, purpose: :variation)
    end
πŸ”Ž See on GitHub

new(transformations)

πŸ“ Source code 
# File activestorage/app/models/active_storage/variation.rb, line 46
  def initialize(transformations)
    @transformations = transformations.deep_symbolize_keys
  end
πŸ”Ž 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.

πŸ“ Source code 
# File activestorage/app/models/active_storage/variation.rb, line 23
    def wrap(variator)
      case variator
      when self
        variator
      when String
        decode variator
      else
        new variator
      end
    end
πŸ”Ž See on GitHub

Instance Public methods

content_type()

πŸ“ Source code 
# File activestorage/app/models/active_storage/variation.rb, line 70
  def content_type
    Marcel::MimeType.for(extension: format.to_s)
  end
πŸ”Ž See on GitHub

default_to(defaults)

πŸ“ Source code 
# File activestorage/app/models/active_storage/variation.rb, line 50
  def default_to(defaults)
    self.class.new transformations.reverse_merge(defaults)
  end
πŸ”Ž See on GitHub

digest()

πŸ“ Source code 
# File activestorage/app/models/active_storage/variation.rb, line 79
  def digest
    OpenSSL::Digest::SHA1.base64digest Marshal.dump(transformations)
  end
πŸ”Ž See on GitHub

format()

πŸ“ Source code 
# File activestorage/app/models/active_storage/variation.rb, line 62
  def format
    transformations.fetch(:format, :png).tap do |format|
      if Marcel::Magic.by_extension(format.to_s).nil?
        raise ArgumentError, "Invalid variant format (#{format.inspect})"
      end
    end
  end
πŸ”Ž See on GitHub

key()

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

πŸ“ Source code 
# File activestorage/app/models/active_storage/variation.rb, line 75
  def key
    self.class.encode(transformations)
  end
πŸ”Ž See on GitHub

transform(file, &block)

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

πŸ“ Source code 
# File activestorage/app/models/active_storage/variation.rb, line 56
  def transform(file, &block)
    ActiveSupport::Notifications.instrument("transform.active_storage") do
      transformer.transform(file, format: format, &block)
    end
  end
πŸ”Ž See on GitHub