Merge pull request #144 from c960657/animated-gif

Add animated? support for png images

lib/fastimage.rb

@@ -436,7 +436,7 @@ def parse_size
 
   def parse_animated
     @type = parse_type unless @type
-    %i(gif webp avif).include?(@type) ? send("parse_animated_for_#{@type}") : nil
+    %i(gif png webp avif).include?(@type) ? send("parse_animated_for_#{@type}") : nil
   end
 
   def fetch_using_base64(uri)
@@ -1096,6 +1096,25 @@ def parse_animated_for_gif
     gif.animated?
   end
 
+  def parse_animated_for_png
+    # Signature (8) + IHDR chunk (4 + 4 + 13 + 4)
+    @stream.read(33)
+
+    loop do
+      length = @stream.read(4).unpack("L>")[0]
+      type = @stream.read(4)
+
+      case type
+      when "acTL"
+        return true
+      when "IDAT"
+        return false
+      end
+
+      @stream.skip(length + 4)
+    end
+  end
+
   def parse_animated_for_webp
     vp8 = @stream.read(16)[12..15]
     _len = @stream.read(4).unpack("V")

test/test.rb

@@ -15,6 +15,7 @@
   "test_v5header.bmp"=>[:bmp, [40, 27]],
   "test.gif"=>[:gif, [17, 32]],
   "animated.gif"=>[:gif, [400, 400]],
+  "animated.png"=>[:png, [100, 100]],
   "animated_without_gct.gif"=>[:gif, [859, 478]],
   "test.jpg"=>[:jpeg, [882, 470]],
   "test.png"=>[:png, [30, 20]],
@@ -123,9 +124,11 @@ def test_should_report_size_correctly
   end
 
   def test_should_report_animated_correctly
-    assert_equal nil, FastImage.animated?(TestUrl + "test.png")
+    assert_equal nil, FastImage.animated?(TestUrl + "test.jpg")
+    assert_equal false, FastImage.animated?(TestUrl + "test.png")
     assert_equal false, FastImage.animated?(TestUrl + "test.gif")
     assert_equal true, FastImage.animated?(TestUrl + "animated.gif")
+    assert_equal true, FastImage.animated?(TestUrl + "animated.png")
     assert_equal true, FastImage.animated?(TestUrl + "animated_without_gct.gif")
     assert_equal false, FastImage.animated?(TestUrl + "webp_vp8x.webp")
     assert_equal true, FastImage.animated?(TestUrl + "webp_animated.webp")