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module FastImageParsing
class IOStream < SimpleDelegator # :nodoc:
include StreamUtil
end
class Jpeg < ImageBase # :nodoc:
def dimensions
exif = nil
state = nil
loop do
state = case state
when nil
@stream.skip(2)
:started
when :started
@stream.read_byte == 0xFF ? :sof : :started
when :sof
case @stream.read_byte
when 0xe1 # APP1
skip_chars = @stream.read_int - 2
data = @stream.read(skip_chars)
io = StringIO.new(data)
if io.read(4) == "Exif"
io.read(2)
new_exif = Exif.new(IOStream.new(io)) rescue nil
exif ||= new_exif # only use the first APP1 segment
end
:started
when 0xe0..0xef
:skipframe
when 0xC0..0xC3, 0xC5..0xC7, 0xC9..0xCB, 0xCD..0xCF
:readsize
when 0xFF
:sof
else
:skipframe
end
when :skipframe
skip_chars = @stream.read_int - 2
@stream.skip(skip_chars)
:started
when :readsize
@stream.skip(3)
height = @stream.read_int
width = @stream.read_int
width, height = height, width if exif && exif.rotated?
return [width, height, exif ? exif.orientation : 1]
end
end
end
end
end
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