Class: HexaPDF::Object

Inherits:
Object
  • Object
show all
Includes:
Comparable
Defined in:
lib/hexapdf/object.rb

Overview

Objects of the PDF object system.

Overview

A PDF object is like a normal object but with an additional *object identifier* consisting of an object number and a generation number. If the object number is zero, then the PDF object represents a direct object. Otherwise the object identifier uniquely identifies this object as an indirect object and can be used for referencing it (from possibly multiple places).

Furthermore a PDF object may have an associated stream. However, this stream is only accessible if the subclass Stream is used.

A PDF object should be connected to a PDF document, otherwise some methods may not work.

Most PDF objects in a PDF document are represented by subclasses of this class that provide additional functionality.

The methods #hash and #eql? are implemented so that objects of this class can be used as hash keys. Furthermore the implementation is compatible to the one of Reference, i.e. the hash of a PDF Object is the same as the hash of its corresponding Reference object.

Allowed PDF Object Values

The PDF specification knows of the following object types:

  • Boolean (mapped to true and false),

  • Integer (mapped to Integer object)

  • Real (mapped to Float objects)

  • String (mapped to String objects with UTF-8 or binary encoding)

  • Names (mapped to Symbol objects)

  • Array (mapped to Array objects)

  • Dictionary (mapped to Hash objects)

  • Stream (mapped to the Stream class which is a Dictionary with the associated stream data)

  • Null (mapped to nil)

  • Indirect Object (mapped to this class)

So working with PDF objects in HexaPDF is rather straightforward since the common Ruby objects can be used for most things, i.e. wrapping an plain Ruby object into an object of this class is not necessary (except if it should become an indirect object).

There are also some additional data structures built from these primitive ones. For example, Time objects are represented as specially formatted string objects and conversion from and to the string representation is handled automatically.

Important: Users of HexaPDF may use other plain Ruby objects but then there is no guarantee that everything will work correctly, especially when using other collection types than arrays and hashes.

See: HexaPDF::Dictionary, HexaPDF::Stream, HexaPDF::Reference, HexaPDF::Document

See: PDF1.7 s7.3.10, s7.3.8

Direct Known Subclasses

Dictionary, Rectangle

Constant Summary collapse

NOT_DUPLICATABLE_CLASSES =

A list of classes whose objects cannot be duplicated.

[NilClass, FalseClass, TrueClass, Symbol, Integer, Float].freeze

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(value, document: nil, oid: nil, gen: nil, stream: nil) ⇒ Object

Creates a new PDF object wrapping the value.

The value can either be a PDFData object in which case it is used directly. If it is a PDF Object, then its data is used. Otherwise the value object is used as is. In all cases, the oid, gen and stream values may be overridden by the corresponding keyword arguments.



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# File 'lib/hexapdf/object.rb', line 162

def initialize(value, document: nil, oid: nil, gen: nil, stream: nil)
  @data = case value
          when PDFData then value
          when Object then value.data
          else PDFData.new(value)
          end
  @data.oid = oid if oid
  @data.gen = gen if gen
  @data.stream = stream if stream
  self.document = document
  self.must_be_indirect = false
  after_data_change
end

Instance Attribute Details

#data ⇒ Object (readonly)

The wrapped HexaPDF::PDFData value.

This attribute is not part of the public API!



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# File 'lib/hexapdf/object.rb', line 149

def data
  @data
end

#document ⇒ Object

Returns the associated PDF document.

If no document is associated, an error is raised.



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# File 'lib/hexapdf/object.rb', line 210

def document
  @document || raise(HexaPDF::Error, "No document associated with this object (#{inspect})")
end

#must_be_indirect=(value) ⇒ Object (writeonly)

Sets whether the object has to be an indirect object once it is written.



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# File 'lib/hexapdf/object.rb', line 155

def must_be_indirect=(value)
  @must_be_indirect = value
end

Class Method Details

.deep_copy(object) ⇒ Object

:call-seq:

HexaPDF::Object.deep_copy(object)    -> copy

Creates a deep copy of the given object which retains the references to indirect objects.



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# File 'lib/hexapdf/object.rb', line 129

def self.deep_copy(object)
  case object
  when Hash
    object.each_with_object({}) {|(key, val), memo| memo[key] = deep_copy(val) }
  when Array
    object.map {|o| deep_copy(o) }
  when HexaPDF::Object
    (object.indirect? || object.must_be_indirect? ? object : deep_copy(object.value))
  when HexaPDF::Reference
    object
  when *NOT_DUPLICATABLE_CLASSES
    object
  else
    object.dup
  end
end

Instance Method Details

#<=>(other) ⇒ Object

Compares this object to another object.

If the other object does not respond to oid or gen, nil is returned. Otherwise objects are ordered first by object number and then by generation number.



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# File 'lib/hexapdf/object.rb', line 291

def <=>(other)
  return nil unless other.respond_to?(:oid) && other.respond_to?(:gen)
  (oid == other.oid ? gen <=> other.gen : oid <=> other.oid)
end

#==(other) ⇒ Object

Returns true if the other object is an Object and wraps the same #data structure.



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# File 'lib/hexapdf/object.rb', line 297

def ==(other)
  other.kind_of?(Object) && data == other.data
end

#deep_copy ⇒ Object

Makes a deep copy of the source PDF object and resets the object identifier.



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# File 'lib/hexapdf/object.rb', line 277

def deep_copy
  obj = dup
  obj.instance_variable_set(:@data, @data.dup)
  obj.data.oid = 0
  obj.data.gen = 0
  obj.data.stream = @data.stream.dup if @data.stream.kind_of?(String)
  obj.data.value = self.class.deep_copy(@data.value)
  obj
end

#document? ⇒ Boolean

Returns true if a PDF document is associated.

Returns:

  • (Boolean) 


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# File 'lib/hexapdf/object.rb', line 215

def document?
  !@document.nil?
end

#eql?(other) ⇒ Boolean

Returns true if the other object references the same PDF object as this object.

Returns:

  • (Boolean) 


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# File 'lib/hexapdf/object.rb', line 302

def eql?(other)
  other.respond_to?(:oid) && oid == other.oid && other.respond_to?(:gen) && gen == other.gen
end

#gen ⇒ Object

Returns the generation number of the PDF object.



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# File 'lib/hexapdf/object.rb', line 187

def gen
  data.gen
end

#gen=(gen) ⇒ Object

Sets the generation number of the PDF object.



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# File 'lib/hexapdf/object.rb', line 192

def gen=(gen)
  data.gen = gen
end

#hash ⇒ Object

Computes the hash value based on the object and generation numbers.



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# File 'lib/hexapdf/object.rb', line 307

def hash
  oid.hash ^ gen.hash
end

#indirect? ⇒ Boolean

Returns true if the object is an indirect object (i.e. has an object number unequal to zero).

Returns:

  • (Boolean) 


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# File 'lib/hexapdf/object.rb', line 221

def indirect?
  oid != 0
end

#inspect ⇒ Object

:nodoc:



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# File 'lib/hexapdf/object.rb', line 311

def inspect #:nodoc:
  "#<#{self.class.name} [#{oid}, #{gen}] value=#{value.inspect}>"
end

#must_be_indirect? ⇒ Boolean

Returns true if the object must be an indirect object once it is written.

Returns:

  • (Boolean) 


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# File 'lib/hexapdf/object.rb', line 226

def must_be_indirect?
  @must_be_indirect
end

#null? ⇒ Boolean

Returns true if the object represents the PDF null object.

Returns:

  • (Boolean) 


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# File 'lib/hexapdf/object.rb', line 246

def null?
  value.nil?
end

#oid ⇒ Object

Returns the object number of the PDF object.



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# File 'lib/hexapdf/object.rb', line 177

def oid
  data.oid
end

#oid=(oid) ⇒ Object

Sets the object number of the PDF object.



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# File 'lib/hexapdf/object.rb', line 182

def oid=(oid)
  data.oid = oid
end

#type ⇒ Object

Returns the type (symbol) of the object.

Since the type system is implemented in such a way as to allow exchanging implementations of specific types, the class of an object can’t be reliably used for determining the actual type.

However, the Type and Subtype fields can easily be used for this. Subclasses for PDF objects that don’t have such fields may use a unique name that has to begin with XX (see PDF1.7 sE.2) and therefore doesn’t clash with names defined by the PDF specification.

For basic objects this always returns :Unknown.



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# File 'lib/hexapdf/object.rb', line 241

def type
  :Unknown
end

#validate(auto_correct: true) ⇒ Object

:call-seq:

obj.validate(auto_correct: true)                               -> true or false
obj.validate(auto_correct: true) {|msg, correctable| block }   -> true or false

Validates the object and, optionally, corrects problems when the option auto_correct is set. The validation routine itself has to be implemented in the #perform_validation method - see its documentation for more information.

If a block is given, it is called on validation problems with a problem description and whether the problem is correctable.

Returns true if the object is deemed valid and false otherwise.

Note: Even if the return value is true there may be problems since HexaPDF doesn’t currently implement the full PDF spec. However, if the return value is false, there is certainly a problem!



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# File 'lib/hexapdf/object.rb', line 266

def validate(auto_correct: true)
  catch do |catch_tag|
    perform_validation do |msg, correctable|
      yield(msg, correctable) if block_given?
      throw(catch_tag, false) unless auto_correct && correctable
    end
    true
  end
end

#value ⇒ Object

Returns the object value.



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# File 'lib/hexapdf/object.rb', line 197

def value
  data.value
end

#value=(val) ⇒ Object

Sets the object value. Unlike in #initialize the value is used as is!



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# File 'lib/hexapdf/object.rb', line 202

def value=(val)
  data.value = val
  after_data_change
end