Class: Exif::Canon

Inherits:
Object
  • Object
show all
Defined in:
lib/exifparser/makernote/canon.rb

Instance Method Summary collapse

Constructor Details

#initialize(fin, tiff_origin, dataPos, byteOrder_module) ⇒ Canon

Returns a new instance of Canon.



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# File 'lib/exifparser/makernote/canon.rb', line 445

def initialize(fin, tiff_origin, dataPos, byteOrder_module)
  @fin = fin
  @tiffHeader0 = tiff_origin
  @dataPos = dataPos
  @byteOrder_module = byteOrder_module
  self.extend @byteOrder_module
end

Instance Method Details

#scan_IFD ⇒ Object 



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# File 'lib/exifparser/makernote/canon.rb', line 453

def scan_IFD
  #
  # Canon MakerNote starts from 0
  #
  @fin.pos = @dataPos + 0
  #
  # get the number of tags
  #
  numDirs = decode_ushort(fin_read_n(2))
  #
  # now scan them
  #
  1.upto(numDirs) {
    curpos_tag = @fin.pos
    tag = parseTagID(fin_read_n(2))
    tagclass = Tag.find(tag.hex, Tag::CanonIFDTable)
    unit, formatter = Tag::Format::Unit[decode_ushort(fin_read_n(2))]
    count = decode_ulong(fin_read_n(4))
    tagdata = fin_read_n(4)
    obj = tagclass.new(tag, "MakerNote", count)
    obj.extend formatter, @byteOrder_module
    obj.pos = curpos_tag
    if unit * count > 4
      curpos = @fin.pos
      begin
        @fin.pos = @tiffHeader0 + decode_ulong(tagdata)
        obj.dataPos = @fin.pos
        obj.data = fin_read_n(unit*count)
      ensure
        @fin.pos = curpos
      end
    else
      obj.dataPos = @fin.pos - 4
      obj.data = tagdata
    end
    obj.processData
    yield obj
  }
end