1 files changed, 45 insertions, 0 deletions
diff --git a/activestorage/lib/active_storage/analyzer/image_analyzer.rb b/activestorage/lib/active_storage/analyzer/image_analyzer.rb
new file mode 100644
index 0000000000..3b39de91be
--- /dev/null
+++ b/activestorage/lib/active_storage/analyzer/image_analyzer.rb
@@ -0,0 +1,45 @@
+# frozen_string_literal: true
+
+module ActiveStorage
+  # Extracts width and height in pixels from an image blob.
+  #
+  # If the image contains EXIF data indicating its angle is 90 or 270 degrees, its width and height are swapped for convenience.
+  #
+  # Example:
+  #
+  #   ActiveStorage::Analyzer::ImageAnalyzer.new(blob).metadata
+  #   # => { width: 4104, height: 2736 }
+  #
+  # This analyzer relies on the third-party {MiniMagick}[https://github.com/minimagick/minimagick] gem. MiniMagick requires
+  # the {ImageMagick}[http://www.imagemagick.org] system library.
+  class Analyzer::ImageAnalyzer < Analyzer
+    def self.accept?(blob)
+      blob.image?
+    end
+
+    def metadata
+      read_image do |image|
+        if rotated_image?(image)
+          { width: image.height, height: image.width }
+        else
+          { width: image.width, height: image.height }
+        end
+      end
+    rescue LoadError
+      logger.info "Skipping image analysis because the mini_magick gem isn't installed"
+      {}
+    end
+
+    private
+      def read_image
+        download_blob_to_tempfile do |file|
+          require "mini_magick"
+          yield MiniMagick::Image.new(file.path)
+        end
+      end
+
+      def rotated_image?(image)
+        %w[ RightTop LeftBottom ].include?(image["%[orientation]"])
+      end
+  end
+end