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# frozen_string_literal: true
# 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")
#
# 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 https://www.imagemagick.org/script/mogrify.php.
class ActiveStorage::Variation
attr_reader :transformations
class << self
# 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.
def wrap(variator)
case variator
when self
variator
when String
decode variator
else
new variator
end
end
# 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 <tt>ActiveStorage::Variant#key</tt>).
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 returned by <tt>MiniMagick::Image.read(io)</tt>,
# and performs the +transformations+ against it. The transformed image instance is then returned.
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
# Returns a signed key for all the +transformations+ that this variation was instantiated with.
def key
self.class.encode(transformations)
end
private
def pass_transform_argument(command, method, argument)
if eligible_argument?(argument)
command.public_send(method, argument)
else
command.public_send(method)
end
end
def eligible_argument?(argument)
argument.present? && argument != true
end
end
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