Class: IPTC::JPEG::Markers::APP13Marker

Inherits:
IPTC::JPEG::Marker show all
Defined in:
lib/iptc/jpeg/markers.rb

Overview

The APP13Marker

The APP13 marker, know as the IPTC Marker See also the IPTC::MarkerNomenclature.

Constant Summary collapse

SHORT = 
1
WORD = 
2
LONG = 
4

Instance Attribute Summary

Attributes inherited from IPTC::JPEG::Marker

#prefix, #values

Instance Method Summary collapse

Methods inherited from IPTC::JPEG::Marker

NewMarker, #l, #read

Constructor Details

#initialize(type, data) ⇒ APP13Marker

Returns a new instance of APP13Marker.



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# File 'lib/iptc/jpeg/markers.rb', line 45

def initialize(type, data)
  @header = "Photoshop 3.0\000"

  super(type, data)
  @prefix = "iptc"

end

Instance Method Details

#[](item) ⇒ Object 



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# File 'lib/iptc/jpeg/markers.rb', line 150

def [](item)
  return @values[item]
end

#long ⇒ Object 



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# File 'lib/iptc/jpeg/markers.rb', line 63

def long
  read(LONG).unpack("N")[0]
end

#parse ⇒ Object 



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# File 'lib/iptc/jpeg/markers.rb', line 67

def parse
  l "APP13 marker parsed"
  @markers = Array.new

  # http://www.fileformat.info/format/psd/egff.htm
  # this one is much up to date.

  while @content.pos < @content.length - 1

    eight_bim = read(LONG)
    # Not a 8BIM packet. Go away !

    if eight_bim != "8BIM"
      l "At #{@content.pos}/#{@content.length} we were unable to find an 8BIM marker (#{eight_bim})."
      return
    end

    @bim_type = word()

    # Read name length and normalize to even number of bytes
    # Weird, always read 4 bytes
    padding = read(4)
    bim_size = word()

    # http://www.sno.phy.queensu.ca/~phil/exiftool/TagNames/Photoshop.html
    case @bim_type 

    when 0x0404 # IPTC
      content = StringIO.new(read(bim_size))

      while !content.eof?

        header = content.read(2).unpack("n")[0]

        # http://www.sno.phy.queensu.ca/~phil/exiftool/TagNames/IPTC.html
        case header
        when 0x1C01
          # skip the envelope
          while !content.eof?
            if content.read(1) == "\x1c"
              content.pos = content.pos - 1
              break
            end
          end
        when 0x1C02

          type = content.read(1).unpack('c')[0]
          size = content.read(2)
          value = content.read(size.unpack('n')[0])

          l "Found marker 0x#{type.to_s(16)}"
          marker = IPTC::Marker.new(type, value)
          k = @prefix+"/"+IPTC::MarkerNomenclature.markers(type.to_i).name
          if @values.has_key?(k)
            if @values[k].is_a?(Array)
              @values[k] << value
            else
              @values[k] = [@values[k], value]
            end
          else
              @values[k] = value
          end
          @markers << marker

        else
          # raise InvalidBlockException.new("Invalid BIM segment #{header.inspect} in marker\n#{@original_content.inspect}")
        end
      end
    when 0x03ED
      hRes = long()
      hResUnit = word()
      widthUnit = word()
      vRes = long()
      vResUnit = word()
      heightUnit = word()
    else
      read(bim_size)
    end
    read(1) if bim_size%2 == 1
  end
  return @values
end

#properties ⇒ Object 



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# File 'lib/iptc/jpeg/markers.rb', line 166

def properties
  return IPTC::TAGS.values.sort
end

#set(property, value) ⇒ Object 



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# File 'lib/iptc/jpeg/markers.rb', line 169

def set(property, value)
  numerical_tag = IPTC::TAGS.index(property)
  if numerical_tag!=nil
  else
    throw InvalidPropertyException.new("Invalid property #{property} for IPTC marker")
  end
  marker = IPTC::Marker.new(numerical_tag, value)
  @markers << marker
end

#to_binary ⇒ Object 



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# File 'lib/iptc/jpeg/markers.rb', line 153

def to_binary
  marker = ""
  @markers.each do |value|
    marker += value.to_binary
  end

  marker =  @header+@bim_type+@bim_dummy+[marker.length].pack('n')+marker

  # build the complete marker
  marker = super(marker)

  return marker
end

#valid? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/iptc/jpeg/markers.rb', line 52

def valid?
  return read(@header.length)==@header
end

#word ⇒ Object 



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# File 'lib/iptc/jpeg/markers.rb', line 60

def word
  read(WORD).unpack("n")[0]
end