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

#initialize(objects, pagenum, options = {}) ⇒ Page

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 33

def initialize(objects, pagenum, options = {})
  @objects, @pagenum = objects, pagenum
  @page_object = objects.deref(objects.page_references[pagenum - 1])
  @cache       = options[:cache] || {}

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

Instance Attribute Details

#cacheObject (readonly)

a Hash-like object for storing cached data. Generally this is scoped to the current document and is used to avoid repeating expensive operations



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# File 'lib/pdf/reader/page.rb', line 26

def cache
  @cache
end

#objectsObject (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

#page_objectObject (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

#attributesObject

Returns the attributes that accompany this page, including attributes inherited from parents.



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# File 'lib/pdf/reader/page.rb', line 58

def attributes
  @attributes ||= {}.tap { |hash|
    page_with_ancestors.reverse.each do |obj|
      hash.merge!(@objects.deref(obj))
    end
  }
  # This shouldn't be necesary, but some non compliant PDFs leave MediaBox
  # out. Assuming 8.5" x 11" is what Acobat does, so we do it too.
  @attributes[:MediaBox] ||= [0,0,612,792]
  @attributes
end

#inspectObject

return a friendly string representation of this page



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# File 'lib/pdf/reader/page.rb', line 51

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

#numberObject

return the number of this page within the full document



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

def number
  @pagenum
end

#orientationObject

Convenience method to identify the page's orientation.



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# File 'lib/pdf/reader/page.rb', line 72

def orientation
  OrientationDetector.new(attributes).orientation
end

#raw_contentObject

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 117

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

#textObject 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 79

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

#walk(*receivers) ⇒ Object

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 109

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