Module: CombinePDF

Defined in:
lib/combine_pdf.rb,
lib/combine_pdf/combine_pdf_pdf.rb,
lib/combine_pdf/combine_pdf_fonts.rb,
lib/combine_pdf/combine_pdf_fonts.rb,
lib/combine_pdf/combine_pdf_filter.rb,
lib/combine_pdf/combine_pdf_parser.rb,
lib/combine_pdf/combine_pdf_decrypt.rb,
lib/combine_pdf/combine_pdf_operations.rb,
lib/combine_pdf/combine_pdf_basic_writer.rb

Overview

This is a pure ruby library to combine/merge, stmap/overlay and number PDF files.

You can also use this library for writing basic text content into new or existing PDF files (For authoring new PDF files look at the Prawn ruby library).

here is the most basic application for the library, a one-liner that combines the PDF files and saves them:

(CombinePDF.new("file1.pdf") << CombinePDF.new("file2.pdf") << CombinePDF.new("file3.pdf")).save("combined.pdf")

Loading PDF data

Loading PDF data can be done from file system or directly from the memory.

Loading data from a file is easy:

pdf = CombinePDF.new("file.pdf")

you can also parse PDF files from memory:

pdf_data = IO.read 'file.pdf' # for this demo, load a file to memory
pdf = CombinePDF.parse(pdf_data)

Loading from the memory is especially effective for importing PDF data recieved through the internet or from a different authoring library such as Prawn.

Combine/Merge PDF files or Pages

To combine PDF files (or data):

pdf = CombinePDF.new
pdf << CombinePDF.new("file1.pdf")
pdf << CombinePDF.new("file2.pdf")
pdf.save "combined.pdf"

as demonstrated above, these can be chained for into a one-liner.

you can also choose to add only specific pages.

in this example, only even pages will be added:

pdf = CombinePDF.new
i = 0
CombinePDF.new("file.pdf").pages.each do |page|
  i += 1
  pdf << page if i.even?
end
pdf.save "even_pages.pdf"

notice that adding the whole file is faster then adding each page seperately.

Add content to existing pages (Stamp / Watermark)

To add content to existing PDF pages, first import the new content from an existing PDF file. after that, add the content to each of the pages in your existing PDF.

in this example, a company logo will be stamped over each page:

 = CombinePDF.new("company_logo.pdf").pages[0]
pdf = CombinePDF.new "content_file.pdf"
pdf.pages.each {|page| page << }
pdf.save "content_with_logo.pdf"

Notice the << operator is on a page and not a PDF object. The << operator acts differently on PDF objects and on Pages.

The << operator defaults to secure injection by renaming references to avoid conflics.

Less recommended, but available - for overlaying pages using compressed data that might not be editable (due to limited filter support), you can use:

pdf.pages(nil, false).each {|page| page << stamp_page}

Page Numbering

adding page numbers to a PDF object or file is as simple as can be:

pdf = CombinePDF.new "file_to_number.pdf"
pdf.number_pages
pdf.save "file_with_numbering.pdf"

numbering can be done with many different options, with different formating, with or without a box object, and even with opacity values.

Writing Content

page numbering actually adds content using the PDFWriter object (a very basic writer).

in this example, all the PDF pages will be stamped, along the top, with a red box, with blue text, stating “Draft, page #”. here is the easy way (we can even use “number_pages” without page numbers, if we wish):

pdf = CombinePDF.new "file_to_stamp.pdf"
pdf.number_pages number_format: " - Draft, page %d - ", number_location: [:top], font_color: [0,0,1], box_color: [0.4,0,0], opacity: 0.75, font_size:16
pdf.save "draft.pdf"

for demntration, it will now be coded the hard way, just so we can play more directly with some of the data.

pdf = CombinePDF.new "file_to_stamp.pdf"
ipage_number = 1
pdf.pages.each do |page|
  # create a "stamp" PDF page with the same size as the target page
  # we will do this because we will use this to center the box in the page
  mediabox = page[:MediaBox]
  # CombinePDF is pointer based...
  # so you can add the stamp to the page and still continue to edit it's content!
  stamp = PDFWriter.new mediabox
  page << stamp
  # set the visible dimensions to the CropBox, if it exists.
  cropbox = page[:CropBox]
  mediabox = cropbox if cropbox
  # set stamp text
  text = " Draft (page %d) " % page_number
  # write the textbox
  stamp.textbox text, x: mediabox[0]+30, y: mediabox[1]+30, width: mediabox[2]-mediabox[0]-60, height: mediabox[3]-mediabox[1]-60, font_color: [0,0,1], font_size: :fit_text, box_color: [0.4,0,0], opacity: 0.5
end
pdf.save "draft.pdf"

font support for the writer is still in the works and is extreamly limited. at the moment it is best to limit the fonts to the 14 standard latin fonts (no unicode).

Decryption & Filters

Some PDF files are encrypted and some are compressed (the use of filters)…

There is very little support for encrypted files and very very basic and limited support for compressed files.

I need help with that.

Comments and file structure

If you want to help with the code, please be aware:

I’m a self learned hobbiest at heart. The documentation is lacking and the comments in the code are poor guidlines.

The code itself should be very straight forward, but feel free to ask whatever you want.

Credit

Caige Nichols wrote an amazing RC4 gem which I used in my code.

I wanted to install the gem, but I had issues with the internet and ended up copying the code itself into the combine_pdf_decrypt class file.

Credit to his wonderful is given here. Please respect his license and copyright… and mine.

License

GPLv3

Defined Under Namespace

Modules: Fonts, PDFFilter, PDFOperations Classes: PDF, PDFDecrypt, PDFParser, PDFWriter

Constant Summary collapse

PRIVATE_HASH_KEYS =

lists the Hash keys used for PDF objects

the CombinePDF library doesn’t use special classes for its objects (PDFPage class, PDFStream class or anything like that).

there is only one PDF class which represents the whole of the PDF file.

this Hash lists the private Hash keys that the CombinePDF library uses to differentiate between complex PDF objects.

[:indirect_reference_id, :indirect_generation_number, :raw_stream_content, :is_reference_only, :referenced_object, :indirect_without_dictionary]

Class Method Summary collapse

Class Method Details

.create_page(mediabox = [0.0, 0.0, 612.0, 792.0]) ⇒ Object

makes a PDFWriter object

PDFWriter objects reresent an empty page and have the method “textbox” that adds content to that page.

PDFWriter objects are used internally for numbering pages (by creating a PDF page with the page number and “stamping” it over the existing page).

::mediabox an Array representing the size of the PDF document. defaults to: [0.0, 0.0, 612.0, 792.0]

if the page is PDFWriter object as a stamp, the final size will be that of the original page.



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# File 'lib/combine_pdf.rb', line 183

def create_page(mediabox = [0.0, 0.0, 612.0, 792.0])
  PDFWriter.new mediabox
end

.new(file_name = "") ⇒ Object

Create an empty PDF object or create a PDF object from a file (parsing the file).

file_name

is the name of a file to be parsed.

Raises:

  • (TypeError) 


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# File 'lib/combine_pdf.rb', line 161

def new(file_name = "")
  raise TypeError, "couldn't parse and data, expecting type String" unless file_name.is_a? String
  return PDF.new() if file_name == ''
  PDF.new( PDFParser.new(  IO.read(file_name).force_encoding(Encoding::ASCII_8BIT) ) )
end

.parse(data) ⇒ Object

Create a PDF object from a raw PDF data (parsing the data).

data

is a string that represents the content of a PDF file.

Raises:

  • (TypeError) 


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# File 'lib/combine_pdf.rb', line 168

def parse(data)
  raise TypeError, "couldn't parse and data, expecting type String" unless data.is_a? String
  PDF.new( PDFParser.new(data) )
end

.register_font(font_name, font_metrics, font_pdf_object, font_cmap = nil) ⇒ Object

adds a correctly formatted font object to the font library.

registered fonts will remain in the library and will only be embeded in PDF objects when they are used by PDFWriter objects (for example, for numbering pages).

this function enables plug-ins to expend the font functionality of CombinePDF.

font_name

a Symbol with the name of the font. if the fonts exists in the library, it will be overwritten!

font_metrics

a Hash of font metrics, of the format char => char_width, boundingbox: [left_x, buttom_y, right_x, top_y] where char == character itself (i.e. “ ” for space). The Hash should contain a special value :missing for the metrics of missing characters. an optional :wy might be supported in the future, for up to down fonts.

font_pdf_object

a Hash in the internal format recognized by CombinePDF, that represents the font object.

font_cmap

a CMap dictionary Hash) which maps unicode characters to the hex CID for the font (i.e. {“a” => “61”, “z” => “7a” }).



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# File 'lib/combine_pdf.rb', line 198

def register_font(font_name, font_metrics, font_pdf_object, font_cmap = nil)
  Fonts.register_font font_name, font_metrics, font_pdf_object, font_cmap
end

.register_font_from_pdf_object(font_name, font_object) ⇒ Object

adds an existing font (from any PDF Object) to the font library.

returns the font on success or false on failure.

VERY LIMITTED SUPPORT:

  • at the moment it only imports Type0 fonts.

  • also, to extract the Hash of the actual font object you were looking for, is not a trivial matter. I do it on the console.

font_name

a Symbol with the name of the font registry. if the fonts exists in the library, it will be overwritten!

font_object

a Hash in the internal format recognized by CombinePDF, that represents the font object.



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# File 'lib/combine_pdf.rb', line 211

def register_font_from_pdf_object font_name, font_object
  Fonts.register_font_from_pdf_object font_name, font_object
end