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lib/pdf_generator.ex
defmodule PdfGenerator do
@vsn "0.3.0"
@moduledoc """
# PdfGenerator
Provides a simple wrapper around [wkhtmltopdf](http://wkhtmltopdf.org) and
[pdftk](https://www.pdflabs.com/tools/pdftk-the-pdf-toolkit/) to generate
possibly encrypted PDFs from an HTML source.
# Configuration (optional)
if no or partial configuration is given, PdfGenerator will search for
executables on path. This will rais an error when wkhtmltopdf cannot be
found.
config :pdf_generator,
wkhtml_path: "/path/to/wkhtmltopdf",
pdftk_path: "/path/to/pdftk",
In your config/config.exs. Add :pdf_generator to your mix.exs:
Note that this is optional but advised to as it will perform a check on
startup whether it can find a suitable wkhtmltopdf executable. It's
generally better to have an app fail at startup than at later runtime.
def application do
[applications: [ .., :pdf_generator, ..], .. ]
end
If you don't want to autostart, issue
PdfGenerator.start wkhtml_path: "/path/to/wkhtml_path"
# System requirements
- wkhtmltopdf
- pdftk (optional, for encrypted PDFs)
- goon (optional, for Porcelain shalle wrapper)
Precompiled **wkhtmltopdf** binaries can be obtained here:
http://wkhtmltopdf.org/downloads.html
**pdftk** should be available as package on your system via
- `apt-get install pdftk` on Debian/Ubuntu
- `brew pdftk` on OSX (you'll need homebrew, of course)
- Install the Exe-Installer on Windows found the project's homepage (link
above)
**goon** is available here:
https://github.com/alco/goon/releases
"""
use Application
alias Porcelain.Result
# See http://elixir-lang.org/docs/stable/elixir/Application.html
# for more information on OTP Applications
def start(_type, _args) do
import Supervisor.Spec, warn: false
children = [
# Define workers and child supervisors to be supervised
# worker(TestApp.Worker, [arg1, arg2, arg3])
worker(
PdfGenerator.PathAgent, [[
wkhtml_path: Application.get_env(:pdf_generator, :wkhtml_path ),
pdftk_path: Application.get_env(:pdf_generator, :pdftk_path ),
]]
)
]
opts = [strategy: :one_for_one, name: PdfGenerator.Supervisor]
Supervisor.start_link(children, opts)
end
# return file name of generated pdf
# requires: Porcelain, Misc.Random
@doc """
Generates a pdf file from given html string. Returns a string containing a
temporary file path for that PDF.
options:
- page_size: output page size, defaults to "A4"
- open_password: password required to open PDF. Will apply encryption to PDF
- edit_password: password required to edit PDF
- shell_params: list of command-line arguments to wkhtmltopdf
see http://wkhtmltopdf.org/usage/wkhtmltopdf.txt for all options
# Examples
pdf_path_1 = PdfGenerator.generate "<html><body><h1>Boom</h1></body></html>"
pdf_path_2 = PdfGenerator.generate(
"<html><body><h1>Boom</h1></body></html>",
page_size: "A5",
open_password: "secret",
edit_password: "g3h31m",
shell_params: [ "--outline", "--outline-depth3", "3" ]
)
"""
def generate( html ) do
generate html, page_size: "A4"
end
def generate( html, options ) do
wkhtml_path = PdfGenerator.PathAgent.get.wkhtml_path
html_file = Path.join System.tmp_dir, Misc.Random.string <> ".html"
File.write html_file, html
pdf_file = Path.join System.tmp_dir, Misc.Random.string <> ".pdf"
shell_params = [
"--page-size", Keyword.get( options, :page_size ) || "A4",
Keyword.get( options, :shell_params ) || [] # will be flattened
]
executable = wkhtml_path
arguments = List.flatten( [ shell_params, html_file, pdf_file ] )
command_prefix = Keyword.get( options, :command_prefix ) || PdfGenerator.PathAgent.get |> Map.get( :command_prefix )
# allow for xvfb-run wkhtmltopdf arg1 arg2
# or sudo wkhtmltopdf ...
{ executable, arguments } =
case command_prefix do
nil -> { executable, arguments }
cmd -> { cmd, [executable] ++ arguments }
end
%Result{ out: _output, status: status, err: error } = Porcelain.exec(
executable, arguments, [in: "", out: :string, err: :string]
)
case status do
0 ->
case Keyword.get options, :open_password do
nil -> { :ok, pdf_file }
user_pw -> encrypt_pdf(
pdf_file,
user_pw,
Keyword.get( options, :edit_password )
)
end
_ -> { :error, error }
end
end
def encrypt_pdf( pdf_input_path, user_pw, owner_pw ) do
pdftk_path = PdfGenerator.PathAgent.get.pdftk_path
if owner_pw == nil, do: owner_pw = Misc.Random.string(16)
if user_pw == nil, do: user_pw = Misc.Random.string(16)
pdf_output_file = Path.join System.tmp_dir, Misc.Random.string <> ".pdf"
%Result{ out: _output, status: status } = Porcelain.exec(
pdftk_path, [
pdf_input_path,
"output", pdf_output_file,
"owner_pw", owner_pw,
"user_pw", user_pw,
"encrypt_128bit",
"allow", "Printing", "CopyContents"
]
)
case status do
0 -> { :ok, pdf_output_file }
_ -> { :error, "Encrpying the PDF via pdftk failed" }
end
end
end