Class: PDF::Reader::Content

Inherits:
Object
  • Object
show all
Defined in:
lib/pdf/reader/content.rb

Overview

Walks the PDF file and calls the appropriate callback methods when something of interest is found.

The callback methods should exist on the receiver object passed into the constructor. Whenever some content is found that will trigger a callback, the receiver is checked to see if the callback is defined.

If it is defined it will be called. If not, processing will continue.

Available Callbacks

The following callbacks are available and should be methods defined on your receiver class. Only implement the ones you need - the rest will be ignored.

Some callbacks will include parameters which will be passed in as an array. For callbacks that supply no paramters, or where you don’t need them, the *params argument can be left off. Some example callback method definitions are:

def begin_document
def end_page
def show_text(string, *params)
def fill_stroke(*params)

You should be able to infer the basic command the callback is reporting based on the name. For further experimentation, define the callback with just a *params parameter, then print out the contents of the array using something like:

puts params.inspect

Text Callbacks

  • end_text_object

  • move_to_start_of_next_line

  • set_character_spacing

  • move_text_position

  • move_text_position_and_set_leading

  • set_text_font_and_size

  • show_text

  • show_text_with_positioning

  • set_text_leading

  • set_text_matrix_and_text_line_matrix

  • set_text_rendering_mode

  • set_text_rise

  • set_word_spacing

  • set_horizontal_text_scaling

  • move_to_next_line_and_show_text

  • set_spacing_next_line_show_text

Graphics Callbacks

  • close_fill_stroke

  • fill_stroke

  • close_fill_stroke_with_even_odd

  • fill_stroke_with_even_odd

  • begin_marked_content_with_pl

  • begin_inline_image

  • begin_marked_content

  • begin_text_object

  • append_curved_segment

  • concatenate_matrix

  • set_stroke_color_space

  • set_nonstroke_color_space

  • set_line_dash

  • set_glyph_width

  • set_glyph_width_and_bounding_box

  • invoke_xobject

  • define_marked_content_with_pl

  • end_inline_image

  • end_marked_content

  • fill_path_with_nonzero

  • fill_path_with_nonzero

  • fill_path_with_even_odd

  • set_gray_for_stroking

  • set_gray_for_nonstroking

  • set_graphics_state_parameters

  • close_subpath

  • set_flatness_tolerance

  • begin_inline_image_data

  • set_line_join_style

  • set_line_cap_style

  • set_cmyk_color_for_stroking,

  • set_cmyk_color_for_nonstroking

  • append_line

  • begin_new_subpath

  • set_miter_limit

  • define_marked_content_point

  • end_path

  • save_graphics_state

  • restore_graphics_state

  • append_rectangle

  • set_rgb_color_for_stroking

  • set_rgb_color_for_nonstroking

  • set_color_rendering_intent

  • close_and_stroke_path

  • stroke_path

  • set_color_for_stroking

  • set_color_for_nonstroking

  • set_color_for_stroking_and_special

  • set_color_for_nonstroking_and_special

  • paint_area_with_shading_pattern

  • append_curved_segment_initial_point_replicated

  • set_line_width

  • set_clipping_path_with_nonzero

  • set_clipping_path_with_even_odd

  • append_curved_segment_final_point_replicated

Misc Callbacks

  • begin_compatibility_section

  • end_compatibility_section,

  • begin_document

  • end_document

  • begin_page_container

  • end_page_container

  • begin_page

  • end_page

Constant Summary collapse

OPERATORS = 
{
  'b'   => :close_fill_stroke,
  'B'   => :fill_stroke,
  'b*'  => :close_fill_stroke_with_even_odd,
  'B*'  => :fill_stroke_with_even_odd,
  'BDC' => :begin_marked_content_with_pl,
  'BI'  => :begin_inline_image,
  'BMC' => :begin_marked_content,
  'BT'  => :begin_text_object,
  'BX'  => :begin_compatibility_section,
  'c'   => :append_curved_segment,
  'cm'  => :concatenate_matrix,
  'CS'  => :set_stroke_color_space,
  'cs'  => :set_nonstroke_color_space,
  'd'   => :set_line_dash,
  'd0'  => :set_glyph_width,
  'd1'  => :set_glyph_width_and_bounding_box,
  'Do'  => :invoke_xobject,
  'DP'  => :define_marked_content_with_pl,
  'EI'  => :end_inline_image,
  'EMC' => :end_marked_content,
  'ET'  => :end_text_object,
  'EX'  => :end_compatibility_section,
  'f'   => :fill_path_with_nonzero,
  'F'   => :fill_path_with_nonzero,
  'f*'  => :fill_path_with_even_odd,
  'G'   => :set_gray_for_stroking,
  'g'   => :set_gray_for_nonstroking,
  'gs'  => :set_graphics_state_parameters,
  'h'   => :close_subpath,
  'i'   => :set_flatness_tolerance,
  'ID'  => :begin_inline_image_data,
  'j'   => :set_line_join_style,
  'J'   => :set_line_cap_style,
  'K'   => :set_cmyk_color_for_stroking,
  'k'   => :set_cmyk_color_for_nonstroking,
  'l'   => :append_line,
  'm'   => :begin_new_subpath,
  'M'   => :set_miter_limit,
  'MP'  => :define_marked_content_point,
  'n'   => :end_path,
  'q'   => :save_graphics_state,
  'Q'   => :restore_graphics_state,
  're'  => :append_rectangle,
  'RG'  => :set_rgb_color_for_stroking,
  'rg'  => :set_rgb_color_for_nonstroking,
  'ri'  => :set_color_rendering_intent,
  's'   => :close_and_stroke_path,
  'S'   => :stroke_path,
  'SC'  => :set_color_for_stroking,
  'sc'  => :set_color_for_nonstroking,
  'SCN' => :set_color_for_stroking_and_special,
  'scn' => :set_color_for_nonstroking_and_special,
  'sh'  => :paint_area_with_shading_pattern,
  'T*'  => :move_to_start_of_next_line,
  'Tc'  => :set_character_spacing,
  'Td'  => :move_text_position,
  'TD'  => :move_text_position_and_set_leading,
  'Tf'  => :set_text_font_and_size,
  'Tj'  => :show_text,
  'TJ'  => :show_text_with_positioning,
  'TL'  => :set_text_leading,
  'Tm'  => :set_text_matrix_and_text_line_matrix,
  'Tr'  => :set_text_rendering_mode,
  'Ts'  => :set_text_rise,
  'Tw'  => :set_word_spacing,
  'Tz'  => :set_horizontal_text_scaling,
  'v'   => :append_curved_segment_initial_point_replicated,
  'w'   => :set_line_width,
  'W'   => :set_clipping_path_with_nonzero,
  'W*'  => :set_clipping_path_with_even_odd,
  'y'   => :append_curved_segment_final_point_replicated,
  '\''  => :move_to_next_line_and_show_text,
  '"'   => :set_spacing_next_line_show_text,
}

Instance Method Summary collapse

Constructor Details

#initialize(receiver, xref) ⇒ Content

Create a new PDF::Reader::Content object to process the contents of PDF file

  • receiver - an object containing the required callback methods

  • xref - a PDF::Reader::Xref object that contains references to all the objects in a PDF file



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# File 'lib/pdf/reader/content.rb', line 221

def initialize (receiver, xref)
  @receiver = receiver
  @xref     = xref
end

Instance Method Details

#callback(name, params = []) ⇒ Object

calls the name callback method on the receiver class with params as the arguments



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# File 'lib/pdf/reader/content.rb', line 282

def callback (name, params=[])
  @receiver.send(name, *params) if @receiver.respond_to?(name)
end

#content_stream(instructions) ⇒ Object

Reads a PDF content stream and calls all the appropriate callback methods for the operators it contains



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# File 'lib/pdf/reader/content.rb', line 255

def content_stream (instructions)
  @buffer = Buffer.new(StringIO.new(instructions))
  @parser = Parser.new(@buffer, @xref)
  @params = [] if @params.nil?

  until @buffer.eof?
    loop do
      token = @parser.parse_token(OPERATORS)

      if token.kind_of?(Token) and OPERATORS.has_key?(token) 
        resolve_resources
        callback(OPERATORS[token], @params)
        @params.clear
        break
      end

      @params << token
    end
  end
rescue EOFError => e
end

#document(root) ⇒ Object

Begin processing the document



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# File 'lib/pdf/reader/content.rb', line 227

def document (root)
  callback(:begin_document, [root])
  walk_pages(@xref.object(root['Pages']))
  callback(:end_document)
end

#resolve_resources ⇒ Object 



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# File 'lib/pdf/reader/content.rb', line 277

def resolve_resources
  # FIXME TODO
end

#walk_pages(page) ⇒ Object

Walk over all pages in the PDF file, calling the appropriate callbacks for each page and all its content



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# File 'lib/pdf/reader/content.rb', line 235

def walk_pages (page)
  if page['Type'] == "Pages"
    callback(:begin_page_container, [page])
    page['Kids'].each {|child| walk_pages(@xref.object(child))}
    callback(:end_page_container)
  elsif page['Type'] == "Page"
    callback(:begin_page, [page])
    @page = page
    @params = []

    page['Contents'].to_a.each do |cstream|
      content_stream(@xref.object(cstream))
    end if page.has_key?('Contents') and page['Contents']

    callback(:end_page)
  end
end