124 lines
3.0 KiB
Ruby
124 lines
3.0 KiB
Ruby
# frozen_string_literal: true
|
|
|
|
class GifReader
|
|
attr_reader :animated
|
|
|
|
EXTENSION_LABELS = [0xf9, 0x01, 0xff].freeze
|
|
GIF_HEADERS = %w(GIF87a GIF89a).freeze
|
|
|
|
class GifReaderException; 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).unpack('C')[0] >= 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).unpack('C')[0])
|
|
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 webm
|
|
class GifTranscoder < Paperclip::Processor
|
|
def make
|
|
return File.open(@file.path) unless needs_convert?
|
|
|
|
final_file = Paperclip::Transcoder.make(file, options, attachment)
|
|
|
|
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]
|
|
|
|
final_file
|
|
end
|
|
|
|
private
|
|
|
|
def needs_convert?
|
|
options[:style] == :original && GifReader.animated?(file.path)
|
|
end
|
|
end
|
|
end
|