Class: FastImageParsing::Jpeg

Inherits:
ImageBase show all
Defined in:
lib/fastimage/fastimage_parsing/jpeg.rb

Overview

:nodoc:

Instance Method Summary collapse

Methods inherited from ImageBase

#animated?, #initialize

Constructor Details

This class inherits a constructor from FastImageParsing::ImageBase

Instance Method Details

#dimensions ⇒ Object 



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# File 'lib/fastimage/fastimage_parsing/jpeg.rb', line 7

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