Revert "Support animated PNGs in media attachments (#28516)" (#33334)

lib/paperclip/blurhash_transcoder.rb

@@ -23,7 +23,7 @@ module Paperclip
         image = Vips::Image.thumbnail(@file.path, 100)
         [image.width, image.height, image.colourspace(:srgb).extract_band(0, n: 3).to_a.flatten]
       else
-        pixels   = convert(':source -flatten -depth 8 -compress none RGB:-', source: File.expand_path(@file.path)).unpack('C*')
+        pixels   = convert(':source -depth 8 RGB:-', source: File.expand_path(@file.path)).unpack('C*')
         geometry = options.fetch(:file_geometry_parser).from_file(@file)
         [geometry.width, geometry.height, pixels]
       end

lib/paperclip/gif_transcoder.rb

@@ -0,0 +1,126 @@
+# frozen_string_literal: true
+
+class GifReader
+  attr_reader :animated
+
+  EXTENSION_LABELS = [0xf9, 0x01, 0xff].freeze
+  GIF_HEADERS      = %w(GIF87a GIF89a).freeze
+
+  class GifReaderException < StandardError; end
+
+  class UnknownImageType < GifReaderException; end
+
+  class CannotParseImage < GifReaderException; end
+
+  def self.animated?(path)
+    new(path).animated
+  rescue GifReaderException
+    false
+  end
+
+  def initialize(path, max_frames = 2)
+    @path      = path
+    @nb_frames = 0
+
+    File.open(path, 'rb') do |s|
+      raise UnknownImageType unless GIF_HEADERS.include?(s.read(6))
+
+      # Skip to "packed byte"
+      s.seek(4, IO::SEEK_CUR)
+
+      # "Packed byte" gives us the size of the GIF color table
+      packed_byte, = s.read(1).unpack('C')
+
+      # Skip background color and aspect ratio
+      s.seek(2, IO::SEEK_CUR)
+
+      if packed_byte & 0x80 != 0
+        # GIF uses a global color table, skip it
+        s.seek(3 * (1 << ((packed_byte & 0x07) + 1)), IO::SEEK_CUR)
+      end
+
+      # Now read data
+      while @nb_frames < max_frames
+        separator = s.read(1)
+
+        case separator
+        when ',' # Image block
+          @nb_frames += 1
+
+          # Skip to "packed byte"
+          s.seek(8, IO::SEEK_CUR)
+          packed_byte, = s.read(1).unpack('C')
+
+          if packed_byte & 0x80 != 0
+            # Image uses a local color table, skip it
+            s.seek(3 * (1 << ((packed_byte & 0x07) + 1)), IO::SEEK_CUR)
+          end
+
+          # Skip lzw min code size
+          raise InvalidValue unless s.read(1).unpack1('C') >= 2
+
+          # Skip image data sub-blocks
+          skip_sub_blocks!(s)
+        when '!' # Extension block
+          skip_extension_block!(s)
+        when ';' # Trailer
+          break
+        else
+          raise CannotParseImage
+        end
+      end
+    end
+
+    @animated = @nb_frames > 1
+  end
+
+  private
+
+  def skip_extension_block!(file)
+    if EXTENSION_LABELS.include?(file.read(1).unpack1('C'))
+      block_size, = file.read(1).unpack('C')
+      file.seek(block_size, IO::SEEK_CUR)
+    end
+
+    # Read until extension block end marker
+    skip_sub_blocks!(file)
+  end
+
+  # Skip sub-blocks up until block end marker
+  def skip_sub_blocks!(file)
+    loop do
+      size, = file.read(1).unpack('C')
+
+      break if size.zero?
+
+      file.seek(size, IO::SEEK_CUR)
+    end
+  end
+end
+
+module Paperclip
+  # This transcoder is only to be used for the MediaAttachment model
+  # to convert animated GIFs to videos
+
+  class GifTranscoder < Paperclip::Processor
+    def make
+      return File.open(@file.path) unless needs_convert?
+
+      final_file = Paperclip::Transcoder.make(file, options, attachment)
+
+      if options[:style] == :original
+        attachment.instance.file_file_name    = "#{File.basename(attachment.instance.file_file_name, '.*')}.mp4"
+        attachment.instance.file_content_type = 'video/mp4'
+        attachment.instance.type              = MediaAttachment.types[:gifv]
+      end
+
+      final_file
+    end
+
+    private
+
+    def needs_convert?
+      GifReader.animated?(file.path)
+    end
+  end
+end

lib/paperclip/gifv_transcoder.rb

@@ -1,20 +0,0 @@
-# frozen_string_literal: true
-
-module Paperclip
-  # This transcoder is only to be used for the MediaAttachment model
-  # to convert animated GIFs and PNGs to videos
-
-  class GifvTranscoder < Paperclip::Processor
-    def make
-      final_file = Paperclip::Transcoder.make(file, options, attachment)
-
-      if options[:style] == :original
-        attachment.instance.file_file_name    = "#{File.basename(attachment.instance.file_file_name, '.*')}.mp4"
-        attachment.instance.file_content_type = 'video/mp4'
-        attachment.instance.type              = MediaAttachment.types[:gifv]
-      end
-
-      final_file
-    end
-  end
-end