Class: HexaPDF::Type::Page

Inherits:
Dictionary show all
Defined in:
lib/hexapdf/type/page.rb

Overview

Represents a page of a PDF document.

A page object contains the meta information for a page. Most of the fields are independent from the page’s content like the /Dur field. However, some of them (like /Resources or /UserUnit) influence how or if the page’s content can be rendered correctly.

A number of field values can also be inherited: /Resources, /MediaBox, /CropBox, /Rotate. Field inheritance means that if a field is not set on the page object itself, the value is taken from the nearest page tree ancestor that has this value set.

See: PDF1.7 s7.7.3.3, s7.7.3.4, Pages

Constant Summary collapse

PAPER_SIZE =

The predefined paper sizes in points (1/72 inch):

  • ISO sizes: A0x4, A0x2, A0-A10, B0-B10, C0-C10

  • Letter, Legal, Ledger, Tabloid, Executive

{
  A0x4: [0, 0, 4768, 6741].freeze,
  A0x2: [0, 0, 3370, 4768].freeze,
  A0: [0, 0, 2384, 3370].freeze,
  A1: [0, 0, 1684, 2384].freeze,
  A2: [0, 0, 1191, 1684].freeze,
  A3: [0, 0, 842, 1191].freeze,
  A4: [0, 0, 595, 842].freeze,
  A5: [0, 0, 420, 595].freeze,
  A6: [0, 0, 298, 420].freeze,
  A7: [0, 0, 210, 298].freeze,
  A8: [0, 0, 147, 210].freeze,
  A9: [0, 0, 105, 147].freeze,
  A10: [0, 0, 74, 105].freeze,
  B0: [0, 0, 2835, 4008].freeze,
  B1: [0, 0, 2004, 2835].freeze,
  B2: [0, 0, 1417, 2004].freeze,
  B3: [0, 0, 1001, 1417].freeze,
  B4: [0, 0, 709, 1001].freeze,
  B5: [0, 0, 499, 709].freeze,
  B6: [0, 0, 354, 499].freeze,
  B7: [0, 0, 249, 354].freeze,
  B8: [0, 0, 176, 249].freeze,
  B9: [0, 0, 125, 176].freeze,
  B10: [0, 0, 88, 125].freeze,
  C0: [0, 0, 2599, 3677].freeze,
  C1: [0, 0, 1837, 2599].freeze,
  C2: [0, 0, 1298, 1837].freeze,
  C3: [0, 0, 918, 1298].freeze,
  C4: [0, 0, 649, 918].freeze,
  C5: [0, 0, 459, 649].freeze,
  C6: [0, 0, 323, 459].freeze,
  C7: [0, 0, 230, 323].freeze,
  C8: [0, 0, 162, 230].freeze,
  C9: [0, 0, 113, 162].freeze,
  C10: [0, 0, 79, 113].freeze,
  Letter: [0, 0, 612, 792].freeze,
  Legal: [0, 0, 612, 1008].freeze,
  Ledger: [0, 0, 792, 1224].freeze,
  Tabloid: [0, 0, 1224, 792].freeze,
  Executive: [0, 0, 522, 756].freeze,
}.freeze
INHERITABLE_FIELDS =

The inheritable fields.

[:Resources, :MediaBox, :CropBox, :Rotate].freeze
REQUIRED_INHERITABLE_FIELDS =

The required inheritable fields.

[:Resources, :MediaBox].freeze

Constants included from DictionaryFields

DictionaryFields::Boolean, DictionaryFields::PDFByteString, DictionaryFields::PDFDate

Constants inherited from Object

Object::NOT_DUPLICATABLE_CLASSES

Instance Attribute Summary

Attributes inherited from Object

#data, #document, #must_be_indirect

Instance Method Summary collapse

Methods inherited from Dictionary

#[]=, define_field, #delete, #each, each_field, #empty?, field, #key?, #to_hash, #type

Methods inherited from Object

#<=>, #==, #deep_copy, deep_copy, #document?, #eql?, #gen, #gen=, #hash, #indirect?, #initialize, #inspect, #null?, #oid, #oid=, #type, #validate, #value, #value=

Constructor Details

This class inherits a constructor from HexaPDF::Object

Instance Method Details

#[](name) ⇒ Object

Returns the value for the entry name.

If name is an inheritable value and the value has not been set on the page object, its value is retrieved from the ancestor page tree nodes.

See: Dictionary#[]



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# File 'lib/hexapdf/type/page.rb', line 151

def [](name)
  if value[name].nil? && INHERITABLE_FIELDS.include?(name)
    node = self
    node = node[:Parent] while node.value[name].nil? && node[:Parent]
    node == self || node.value[name].nil? ? super : node[name]
  else
    super
  end
end

#box(type = :media) ⇒ Object

Returns the rectangle defining a certain kind of box for the page.

This method should be used instead of directly accessing any of /MediaBox, /CropBox, /BleedBox, /ArtBox or /TrimBox because it also takes the fallback values into account!

The following types are allowed:

:media

The media box defines the boundaries of the medium the page is to be printed on.

:crop

The crop box defines the region to which the contents of the page should be clipped when it is displayed or printed. The default is the media box.

:bleed

The bleed box defines the region to which the contents of the page should be clipped when output in a production environment. The default is the crop box.

:trim

The trim box defines the intended dimensions of the page after trimming. The default value is the crop box.

:art

The art box defines the region of the page’s meaningful content as intended by the author. The default is the crop box.

See: PDF1.7 s14.11.2



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# File 'lib/hexapdf/type/page.rb', line 199

def box(type = :media)
  case type
  when :media then self[:MediaBox]
  when :crop then self[:CropBox] || self[:MediaBox]
  when :bleed then self[:BleedBox] || self[:CropBox] || self[:MediaBox]
  when :trim then self[:TrimBox] || self[:CropBox] || self[:MediaBox]
  when :art then self[:ArtBox] || self[:CropBox] || self[:MediaBox]
  else
    raise ArgumentError, "Unsupported page box type provided: #{type}"
  end
end

#canvas(type: :page) ⇒ Object

Returns the requested type of canvas for the page.

The canvas object is cached once it is created so that its graphics state is correctly retained without the need for parsing its contents.

type

Can either be

  • :page for getting the canvas for the page itself (only valid for initially empty pages)

  • :overlay for getting the canvas for drawing over the page contents

  • :underlay for getting the canvas for drawing unter the page contents



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# File 'lib/hexapdf/type/page.rb', line 277

def canvas(type: :page)
  unless [:page, :overlay, :underlay].include?(type)
    raise ArgumentError, "Invalid value for 'type', expected: :page, :underlay or :overlay"
  end
  cache_key = "#{type}_canvas".intern
  return document.cache(@data, cache_key) if document.cached?(@data, cache_key)

  if type == :page && key?(:Contents)
    raise HexaPDF::Error, "Cannot get the canvas for a page with contents"
  end

  contents = self[:Contents]
  if contents.nil?
    page_canvas = document.cache(@data, :page_canvas, Content::Canvas.new(self))
    self[:Contents] = document.add({Filter: :FlateDecode},
                                   stream: page_canvas.stream_data)
  end

  if type == :overlay || type == :underlay
    underlay_canvas = document.cache(@data, :underlay_canvas, Content::Canvas.new(self))
    overlay_canvas = document.cache(@data, :overlay_canvas, Content::Canvas.new(self))

    stream = HexaPDF::StreamData.new do
      Fiber.yield(" q ")
      fiber = underlay_canvas.stream_data.fiber
      while fiber.alive? && (data = fiber.resume)
        Fiber.yield(data)
      end
      " Q q "
    end
    underlay = document.add({Filter: :FlateDecode}, stream: stream)

    stream = HexaPDF::StreamData.new do
      Fiber.yield(" Q ")
      fiber = overlay_canvas.stream_data.fiber
      while fiber.alive? && (data = fiber.resume)
        Fiber.yield(data)
      end
    end
    overlay = document.add({Filter: :FlateDecode}, stream: stream)

    self[:Contents] = [underlay, *self[:Contents], overlay]
  end

  document.cache(@data, cache_key)
end

#contents ⇒ Object

Returns the concatenated stream data from the content streams as binary string.

Note: Any modifications done to the returned value *won’t* be reflected in any of the streams’ data!



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# File 'lib/hexapdf/type/page.rb', line 215

def contents
  Array(self[:Contents]).each_with_object("".b) do |content_stream, content|
    content << " ".freeze unless content.empty?
    content << document.deref(content_stream).stream
  end
end

#contents=(data) ⇒ Object

Replaces the contents of the page with the given string.

This is done by deleting all but the first content stream and reusing this content stream; or by creating a new one if no content stream exists.



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# File 'lib/hexapdf/type/page.rb', line 226

def contents=(data)
  first, *rest = self[:Contents]
  rest.each {|stream| document.delete(stream)}
  if first
    self[:Contents] = first
    document.deref(first).stream = data
  else
    self[:Contents] = document.add({Filter: :FlateDecode}, stream: data)
  end
end

#copy_inherited_values ⇒ Object

Copies the page’s inherited values from the ancestor page tree nodes into a hash and returns the hash.

The hash can then be used to update the page itself (e.g. when moving a page from one position to another) or another page (e.g. when importing a page from another document).



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# File 'lib/hexapdf/type/page.rb', line 166

def copy_inherited_values
  INHERITABLE_FIELDS.each_with_object({}) do |name, hash|
    hash[name] = HexaPDF::Object.deep_copy(self[name]) if value[name].nil?
  end
end

#index ⇒ Object

Returns the index of the page in the page tree.



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# File 'lib/hexapdf/type/page.rb', line 253

def index
  idx = 0
  node = self
  while (parent_node = node[:Parent])
    parent_node[:Kids].each do |kid|
      kid = document.deref(kid)
      break if kid.data == node.data
      idx += (kid.type == :Page ? 1 : kid[:Count])
    end
    node = parent_node
  end
  idx
end

#must_be_indirect? ⇒ Boolean

Returns true since page objects must always be indirect.

Returns:



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# File 'lib/hexapdf/type/page.rb', line 141

def must_be_indirect?
  true
end

#process_contents(processor) ⇒ Object

Processes the content streams associated with the page with the given processor object.

See: HexaPDF::Content::Processor



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# File 'lib/hexapdf/type/page.rb', line 246

def process_contents(processor)
  self[:Resources] = {} if self[:Resources].nil?
  processor.resources = self[:Resources]
  Content::Parser.parse(contents, processor)
end

#resources ⇒ Object

Returns the possibly inherited resource dictionary which is automatically created if it doesn’t exist.



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# File 'lib/hexapdf/type/page.rb', line 239

def resources
  self[:Resources] ||= document.wrap({}, type: :XXResources)
end

#to_form_xobject(reference: true) ⇒ Object

Creates a Form XObject from the page’s dictionary and contents for the given PDF document.

If reference is true, the page’s contents is referenced when possible to avoid unnecessary decoding/encoding.

Note 1: The created Form XObject is not added to the document automatically!

Note 2: If reference is false and if a canvas is used on this page (see #canvas), this method should only be called once the contents of the page has been fully defined. The reason is that during the copying of the content stream data the contents may be modified to make it a fully valid content stream.



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# File 'lib/hexapdf/type/page.rb', line 335

def to_form_xobject(reference: true)
  first, *rest = self[:Contents]
  stream = if !first
             nil
           elsif !reference || !rest.empty? || first.raw_stream.kind_of?(String)
             contents
           else
             first.raw_stream
           end
  dict = {
    Type: :XObject,
    Subtype: :Form,
    BBox: HexaPDF::Object.deep_copy(box(:crop)),
    Resources: HexaPDF::Object.deep_copy(self[:Resources]),
    Filter: :FlateDecode,
  }
  document.wrap(dict, stream: stream)
end