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diff --git a/activestorage/app/models/active_storage/variation.rb b/activestorage/app/models/active_storage/variation.rb
new file mode 100644
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+++ b/activestorage/app/models/active_storage/variation.rb
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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_to_fit: [100, 100], monochrome: true, trim: true, rotate: "-90")
+#
+# The options map directly to {ImageProcessing}[https://github.com/janko-m/image_processing] commands.
+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 a File object, performs the +transformations+ against it, and
+  # saves the transformed image into a temporary file. If +format+ is specified
+  # it will be the format of the result image, otherwise the result image
+  # retains the source format.
+  def transform(file, format: nil, &block)
+    ActiveSupport::Notifications.instrument("transform.active_storage") do
+      transformer.transform(file, format: format, &block)
+    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 transformer
+      if ActiveStorage.variant_processor
+        begin
+          require "image_processing"
+        rescue LoadError
+          ActiveSupport::Deprecation.warn <<~WARNING
+            Generating image variants will require the image_processing gem in Rails 6.1.
+            Please add `gem 'image_processing', '~> 1.2'` to your Gemfile.
+          WARNING
+
+          ActiveStorage::Transformers::MiniMagickTransformer.new(transformations)
+        else
+          ActiveStorage::Transformers::ImageProcessingTransformer.new(transformations)
+        end
+      else
+        ActiveStorage::Transformers::MiniMagickTransformer.new(transformations)
+      end
+    end
+end