Extract metadata from images and videos

3 files changed, 128 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..b25d2092b9
--- /dev/null
+++ b/activestorage/lib/active_storage/analyzer/image_analyzer.rb
@@ -0,0 +1,36 @@
+# frozen_string_literal: true
+
+module ActiveStorage
+  # Extracts width and height in pixels from an image blob.
+  #
+  # 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. These libraries are not provided by Rails; you must
+  # install them yourself to use this analyzer.
+  class Analyzer::ImageAnalyzer < Analyzer
+    def self.accept?(blob)
+      blob.image?
+    end
+
+    def metadata
+      read_image do |image|
+        { width: image.width, height: image.height }
+      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
+  end
+end
diff --git a/activestorage/lib/active_storage/analyzer/null_analyzer.rb b/activestorage/lib/active_storage/analyzer/null_analyzer.rb
new file mode 100644
index 0000000000..8ff7ce48e5
--- /dev/null
+++ b/activestorage/lib/active_storage/analyzer/null_analyzer.rb
@@ -0,0 +1,13 @@
+# frozen_string_literal: true
+
+module ActiveStorage
+  class Analyzer::NullAnalyzer < Analyzer # :nodoc:
+    def self.accept?(blob)
+      true
+    end
+
+    def metadata
+      {}
+    end
+  end
+end
diff --git a/activestorage/lib/active_storage/analyzer/video_analyzer.rb b/activestorage/lib/active_storage/analyzer/video_analyzer.rb
new file mode 100644
index 0000000000..408b5e58e9
--- /dev/null
+++ b/activestorage/lib/active_storage/analyzer/video_analyzer.rb
@@ -0,0 +1,79 @@
+# frozen_string_literal: true
+
+require "active_support/core_ext/hash/compact"
+
+module ActiveStorage
+  # Extracts the following from a video blob:
+  #
+  # * Width (pixels)
+  # * Height (pixels)
+  # * Duration (seconds)
+  # * Angle (degrees)
+  # * Aspect ratio
+  #
+  # Example:
+  #
+  #   ActiveStorage::VideoAnalyzer.new(blob).metadata
+  #   # => { width: 640, height: 480, duration: 5.0, angle: 0, aspect_ratio: [4, 3] }
+  #
+  # This analyzer requires the {ffmpeg}[https://www.ffmpeg.org] system library, which is not provided by Rails. You must
+  # install ffmpeg yourself to use this analyzer.
+  class Analyzer::VideoAnalyzer < Analyzer
+    def self.accept?(blob)
+      blob.video?
+    end
+
+    def metadata
+      { width: width, height: height, duration: duration, angle: angle, aspect_ratio: aspect_ratio }.compact
+    end
+
+    private
+      def width
+        Integer(video_stream["width"]) if video_stream["width"]
+      end
+
+      def height
+        Integer(video_stream["height"]) if video_stream["height"]
+      end
+
+      def duration
+        Float(video_stream["duration"]) if video_stream["duration"]
+      end
+
+      def angle
+        Integer(tags["rotate"]) if tags["rotate"]
+      end
+
+      def aspect_ratio
+        if descriptor = video_stream["display_aspect_ratio"]
+          descriptor.split(":", 2).collect(&:to_i)
+        end
+      end
+
+
+      def tags
+        @tags ||= video_stream["tags"] || {}
+      end
+
+      def video_stream
+        @video_stream ||= streams.detect { |stream| stream["codec_type"] == "video" } || {}
+      end
+
+      def streams
+        probe["streams"] || []
+      end
+
+      def probe
+        download_blob_to_tempfile { |file| probe_from(file) }
+      end
+
+      def probe_from(file)
+        IO.popen([ "ffprobe", "-print_format", "json", "-show_streams", "-v", "error", file.path ]) do |output|
+          JSON.parse(output.read)
+        end
+      rescue Errno::ENOENT
+        logger.info "Skipping video analysis because ffmpeg isn't installed"
+        {}
+      end
+  end
+end