class ActiveStorage::Variation

A list of all possible transformations is available at www.imagemagick.org/script/mogrify.php.
})
crop: “100x100+0+0”,
gravity: “center”,
resize: “100x100^”,
ActiveStorage::Variation.new(combine_options: {
You can also combine multiple transformations in one step, e.g. for center-weighted cropping:
ActiveStorage::Variation.new(resize: “100x100”, monochrome: true, trim: true, rotate: “-90”)
the key is the command and the value is the arguments. Example:
In case you do need to use this directly, it’s instantiated using a hash of transformations where
the ActiveStorage::Blob#variant method and should rarely be used directly.
A set of transformations that can be applied to a blob to create a variant. This class is exposed via

def decode(key)

Returns a Variation instance with the transformations that were encoded by +encode+. 
def decode(key)
  new ActiveStorage.verifier.verify(key, purpose: :variation)
end

def eligible_argument?(argument) 

def eligible_argument?(argument)
  argument.present? && argument != true
end

def encode(transformations)

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

def initialize(transformations) 

def initialize(transformations)
  @transformations = transformations
end

def key

Returns a signed key for all the +transformations+ that this variation was instantiated with. 
def key
  self.class.encode(transformations)
end

def pass_transform_argument(command, method, argument) 

def pass_transform_argument(command, method, argument)
  if eligible_argument?(argument)
    command.public_send(method, argument)
  else
    command.public_send(method)
  end
end

def transform(image)

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

def validate_arg_array(argument) 

def validate_arg_array(argument)
  argument.each do |arg|
    if arg.is_a?(Integer) || arg.is_a?(Float)
      next
    elsif arg.is_a?(String) || arg.is_a?(Symbol)
      validate_arg_string(arg)
    elsif arg.is_a?(Array)
      validate_arg_array(arg)
    elsif arg.is_a?(Hash)
      validate_arg_hash(arg)
    end
  end
end

def validate_arg_hash(argument) 

def validate_arg_hash(argument)
  argument.each do |key, value|
    validate_arg_string(key)
    if value.is_a?(Integer) || value.is_a?(Float)
      next
    elsif value.is_a?(String) || value.is_a?(Symbol)
      validate_arg_string(value)
    elsif value.is_a?(Array)
      validate_arg_array(value)
    elsif value.is_a?(Hash)
      validate_arg_hash(value)
    end
  end
end

def validate_arg_string(argument) 

def validate_arg_string(argument)
  if UNSUPPORTED_IMAGE_PROCESSING_ARGUMENTS.any? { |bad_arg| argument.to_s.downcase.include?(bad_arg) }; raise UnsupportedImageProcessingArgument end
end

def validate_transformation(name, argument) 

def validate_transformation(name, argument)
  method_name = name.to_s.gsub("-","_")
  unless SUPPORTED_IMAGE_PROCESSING_METHODS.any? { |method| method_name == method }
    raise UnsupportedImageProcessingMethod, <<~ERROR.squish
      One or more of the provided transformation methods is not supported.
    ERROR
  end
  if argument.present?
    if argument.is_a?(String) || argument.is_a?(Symbol)
      validate_arg_string(argument)
    elsif argument.is_a?(Array)
      validate_arg_array(argument)
    elsif argument.is_a?(Hash)
      validate_arg_hash(argument)
    end
  end
end

def wrap(variator)

it is assumed to be a transformations Hash and is passed directly to the constructor.
returned unmodified. If it is a String, it is passed to ActiveStorage::Variation.decode. Otherwise,
Returns a Variation instance based on the given variator. If the variator is a Variation, it is 
def wrap(variator)
  case variator
  when self
    variator
  when String
    decode variator
  else
    new variator
  end
end