Add analyze methods for getting metadata

Besides processing images it would be nice to analyze images as well to
get metadata like: width, height and rotation.
This is currently based on the ActiveStorage::Analyzer::ImageAnalyzer.

lib/image_processing.rb

@@ -1,6 +1,7 @@
 require "image_processing/chainable"
 require "image_processing/builder"
 require "image_processing/pipeline"
+require "image_processing/analyzer"
 require "image_processing/processor"
 require "image_processing/version"
 

lib/image_processing/analyzer.rb

@@ -0,0 +1,12 @@
+module ImageProcessing
+  # Abstract class inherited by individual analyzers.
+  class Analyzer
+    def initialize(image)
+      @image = image
+    end
+
+    def analyze
+      { width: @image.width, height: @image.height, rotated: rotated? }
+    end
+  end
+end

lib/image_processing/mini_magick.rb

@@ -16,6 +16,27 @@ def self.valid_image?(file)
       false
     end
 
+    def self.analyze(file)
+      if valid_image?(file)
+        image = ::MiniMagick::Image.new(file.path)
+        Analyzer.new(image).analyze
+      else
+        {}
+      end
+    end
+
+    class Analyzer < ImageProcessing::Analyzer
+      ROTATIONS = %w[ RightTop LeftBottom TopRight BottomLeft ]
+
+      private
+
+      def rotated?
+        ROTATIONS.include?(@image["%[orientation]"])
+      rescue ::MiniMagick::Error
+        false
+      end
+    end
+
     class Processor < ImageProcessing::Processor
       accumulator :magick, ::MiniMagick::Tool
 

lib/image_processing/vips.rb

@@ -6,6 +6,7 @@
 module ImageProcessing
   module Vips
     extend Chainable
+    ROTATIONS = /Right-top|Left-bottom|Top-right|Bottom-left/
 
     # Returns whether the given image file is processable.
     def self.valid_image?(file)
@@ -15,6 +16,27 @@ def self.valid_image?(file)
       false
     end
 
+    def self.analyze(file)
+      if valid_image?(file)
+        image = ::Vips::Image.new_from_file(file.path, access: :sequential)
+        Analyzer.new(image).analyze
+      else
+        {}
+      end
+    end
+
+    class Analyzer < ImageProcessing::Analyzer
+      ROTATIONS = /Right-top|Left-bottom|Top-right|Bottom-left/
+
+      private
+
+      def rotated?
+        ROTATIONS === @image.get("exif-ifd0-Orientation")
+      rescue ::Vips::Error
+        false
+      end
+    end
+
     class Processor < ImageProcessing::Processor
       accumulator :image, ::Vips::Image
 

test/mini_magick_test.rb

@@ -106,6 +106,24 @@
     assert_dimensions [300, 400], pipeline.loader(geometry: "400x400").call
   end unless ENV["GM"]
 
+  it "analyzes the image" do
+    result = ImageProcessing::MiniMagick.analyze(@portrait)
+    expected = { width: 600, height: 800, rotated: false }
+    assert_equal expected, result
+  end
+
+  it "analyzes the rotated image" do
+    result = ImageProcessing::MiniMagick.analyze(fixture_image("rotated.jpg"))
+    expected = { width: 800, height: 600, rotated: true }
+    assert_equal expected, result
+  end
+
+  it "does not analyze an invalid image" do
+    result = ImageProcessing::MiniMagick.analyze(fixture_image("invalid.jpg"))
+    expected = {}
+    assert_equal expected, result
+  end
+
   it "auto orients by default" do
     result = ImageProcessing::MiniMagick.call(fixture_image("rotated.jpg"))
     assert_dimensions [600, 800], result

test/vips_test.rb

@@ -76,6 +76,24 @@
     assert_dimensions [600, 800], result
   end
 
+  it "analyzes a image" do
+    result = ImageProcessing::Vips.analyze(@portrait)
+    expected = { width: 600, height: 800, rotated: false }
+    assert_equal expected, result
+  end
+
+  it "analyzes a rotated image" do
+    result = ImageProcessing::Vips.analyze(fixture_image("rotated.jpg"))
+    expected = { width: 800, height: 600, rotated: true }
+    assert_equal expected, result
+  end
+
+  it "does not analyze an invalid image" do
+    result = ImageProcessing::Vips.analyze(fixture_image("invalid.jpg"))
+    expected = {}
+    assert_equal expected, result
+  end
+
   it "applies loader options" do
     result = ImageProcessing::Vips.loader(shrink: 2).call(@portrait)
     assert_dimensions [300, 400], result