Class: PDF::Reader::Page

Inherits:
Object
  • Object
show all
Includes:
ResourceMethods
Defined in:
lib/pdf/reader/page.rb

Overview

high level representation of a single PDF page. Ties together the various low level classes in PDF::Reader and provides access to the various components of the page (text, images, fonts, etc) in convenient formats.

If you require access to the raw PDF objects for this page, you can access the Page dictionary via the page_object accessor. You will need to use the objects accessor to help walk the page dictionary in any useful way.

Instance Attribute Summary (collapse)

Instance Method Summary (collapse)

Methods included from ResourceMethods

#color_spaces, #fonts, #graphic_states, #patterns, #procedure_sets, #properties, #shadings, #xobjects

Constructor Details

- (Page) initialize(objects, pagenum)

creates a new page wrapper.

  • objects - an ObjectHash instance that wraps a PDF file

  • pagenum - an int specifying the page number to expose. 1 indexed.



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# File 'lib/pdf/reader/page.rb', line 28

def initialize(objects, pagenum)
  @objects, @pagenum = objects, pagenum
  @page_object = objects.deref(objects.page_references[pagenum - 1])

  unless @page_object.is_a?(::Hash)
    raise ArgumentError, "invalid page: #{pagenum}"
  end
end

Instance Attribute Details

- (Object) objects (readonly)

lowlevel hash-like access to all objects in the underlying PDF



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# File 'lib/pdf/reader/page.rb', line 18

def objects
  @objects
end

- (Object) page_object (readonly)

the raw PDF object that defines this page



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# File 'lib/pdf/reader/page.rb', line 21

def page_object
  @page_object
end

Instance Method Details

- (Object) attributes

Returns the attributes that accompany this page. Includes attributes inherited from parents.



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# File 'lib/pdf/reader/page.rb', line 52

def attributes
  {}.tap { |hash|
    page_with_ancestors.reverse.each do |obj|
      hash.merge!(@objects.deref(obj))
    end
  }
end

- (Object) inspect

return a friendly string representation of this page



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# File 'lib/pdf/reader/page.rb', line 45

def inspect
  "<PDF::Reader::Page page: #{@pagenum}>"
end

- (Object) number

return the number of this page within the full document



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# File 'lib/pdf/reader/page.rb', line 39

def number
  @pagenum
end

- (Object) raw_content

returns the raw content stream for this page. This is plumbing, nothing to see here unless you're a PDF nerd like me.



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# File 'lib/pdf/reader/page.rb', line 101

def raw_content
  contents = objects.deref(@page_object[:Contents])
  [contents].flatten.compact.map { |obj|
    objects.deref(obj)
  }.map { |obj|
    obj.unfiltered_data
  }.join
end

- (Object) text Also known as: to_s

returns the plain text content of this page encoded as UTF-8. Any characters that can't be translated will be returned as a ▯



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# File 'lib/pdf/reader/page.rb', line 63

def text
  receiver = PageTextReceiver.new
  walk(receiver)
  receiver.content
end

- (Object) walk(*receivers)

processes the raw content stream for this page in sequential order and passes callbacks to the receiver objects.

This is mostly low level and you can probably ignore it unless you need access to something like the raw encoded text. For an example of how this can be used as a basis for higher level functionality, see the text() method

If someone was motivated enough, this method is intended to provide all the data required to faithfully render the entire page. If you find some required data isn't available it's a bug - let me know.

Many operators that generate callbacks will reference resources stored in the page header - think images, fonts, etc. To facilitate these operators, the first available callback is page=. If your receiver accepts that callback it will be passed the current PDF::Reader::Page object. Use the Page#resources method to grab any required resources.

It may help to think of each page as a self contained program made up of a set of instructions and associated resources. Calling walk() executes the program in the correct order and calls out to your implementation.



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# File 'lib/pdf/reader/page.rb', line 93

def walk(*receivers)
  callback(receivers, :page=, [self])
  content_stream(receivers, raw_content)
end