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require "active_support/core_ext/object/inclusion"
# 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")
#
# A list of all possible transformations is available at https://www.imagemagick.org/script/mogrify.php.
class ActiveStorage::Variation
attr_reader :transformations
class << self
# Returns a variation instance with the transformations that were encoded by `#encode`.
def decode(key)
new ActiveStorage.verifier.verify(key, purpose: :variation)
end
# 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`).
def encode(transformations)
ActiveStorage.verifier.generate(transformations, purpose: :variation)
end
end
def initialize(transformations)
@transformations = transformations
end
# Accepts an open MiniMagick image instance, like what's return by `MiniMagick::Image.read(io)`,
# and performs the `transformations` against it. The transformed image instance is then returned.
def transform(image)
transformations.each do |(method, argument)|
if eligible_argument?(argument)
image.public_send(method, argument)
else
image.public_send(method)
end
end
end
# Returns a signed key for all the `transformations` that this variation was instantiated with.
def key
self.class.encode(transformations)
end
private
def eligible_argument?(argument)
argument.present? && argument != true
end
end
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