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A simple wrapper for wkhtmltopdf (HTML to PDF) for use in Elixir projects.

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elixir-pdf-generator

A wrapper for both wkhtmltopdf and chrome-headless plus PDFTK (adds in encryption) for use in Elixir projects.

{:ok, pdf} = PdfGenerator.generate_binary("<html><body><h1>Yay!</h1></body></html>")

Latest release v0.5.5 – v0.5.7 on 2019-06-18

  • 0.5.7
    • BUGFIX: fix chrome-option parameter handling
  • 0.5.6
    • BUGFIX: fix A4 and A5 paper sizes in inches for chrome-headless: it's not 8.5 x 11.0 (US letter) but 8.26772 x 11.695 (DIN A4), the former being chrome-headless defaults. This is important if you want to create proper A4 pages
    • Users printing US letter sized PDFs, please use page_size: :letter
  • 0.5.5
    • improved documentation on prefer_system_executable: true for chrome. Thanks to Martin Richer for rasining this and a PR
    • improved documentation on no_sandbox: true for chrome in dockerized environment (running as root)
    • clarify that wkhtmltopdf installation snippet is for Ubuntu 18.04.
    • log call options as debug info to Logger
    • add "knows issues" section to README

For a proper changelog, see CHANGES

System prerequisites

It's either

  • wkhtmltopdf or

  • nodejs and possibly chrome/chromium

chrome-headless

This will allow you to make more use of Javascript and advanced CSS as it's just your Chrome/Chromium browser rendering your web page as HTML and printing it as PDF. Rendering tend to be a bit faster than with wkhtmltopdf. The price tag is that PDFs printed with chrome/chromium are usually considerably bigger than those generated with wkhtmltopdf.

  1. Run npm -g install chrome-headless-render-pdf puppeteer.

    This requires nodejs, of course. This will install a recent chromium and chromedriver to run Chrome in headless mode and use this browser and its API to print PDFs globally on your machine.

    If you prefer a project-local install, just use npm install This will install dependencies under ./node_modules. Be aware that those won't be packaged in your distribution (I will add support for this later).

    On some machines, this doesn't install Chromium and fails. Here's how to get this running on Ubuntu 18:

    DEBIAN_FRONTEND=noninteractive PUPPETEER_SKIP_CHROMIUM_DOWNLOAD=TRUE \
  apt-get install -y chromium-chromedriver \
  && npm -g install chrome-headless-render-pdf puppeteer

wkhtmltopdf

  1. Download wkhtmltopdf and place it in your $PATH. Current binaries can be found here: http://wkhtmltopdf.org/downloads.html

    For the impatient (Ubuntu 18.04 Bionic Beaver):

    apt-get -y install xfonts-base xfonts-75dpi \
 && wget https://downloads.wkhtmltopdf.org/0.12/0.12.5/wkhtmltox_0.12.5-1.bionic_amd64.deb \
 && dpkg -i wkhtmltox_0.12.5-1.bionic_amd64.deb

    For other distributions, refer to http://wkhtmltopdf.org/downloads.html – For example, replace bionic with xenial if you're on Ubuntu 16.04.

optional dependencies

  1. optional: Install xvfb (shouldn't be required with the binary mentioned above):

    To use other wkhtmltopdf executables comiled with an unpatched Qt on systems without an X window server installed, please install xvfb-run from your repository (on Debian/Ubuntu: sudo apt-get install xvfb).

    I haven't heard any feedback of people using this feature since a while since the wkhtmltopdf projects ships ready-made binaries. I will deprecate this starting in 0.6.0 since, well, YAGNI.

  2. optional: Install pdftk via your package manager or homebrew. The project page also contains a Windows installer. On Debian/Ubuntu just type: apt-get -y install pdftk

Usage

Add this to your dependencies in your mix.exs:

    def application do
        [applications: [
            :logger,
            :pdf_generator # <-- add this
        ]]
    end

    defp deps do
        [
            # ... whatever else
            { :pdf_generator, ">=0.5.5" }, # <-- and this
        ]
    end

Then pass some html to PdfGenerator.generate

$ iex -S mix

html = "<html><body><p>Hi there!</p></body></html>"
# be aware, this may take a while...
{:ok, filename}    = PdfGenerator.generate(html, page_size: "A5")
{:ok, pdf_content} = File.read(filename)

# or, if you prefer methods that raise on error:
filename = PdfGenerator.generate!(html, generator: :chrome)

Or, pass some URL

PdfGenerator.generate {:url, "http://google.com"}, page_size: "A5"

Or, use chrome-headless – if you're (most probably) using this as dependency, chrome won't be installed to this project directory but globally. We currently need to tell PdfGenerator this by setting the prefer_system_executable: true option. This will be default by v0.6.0.

html_works_too = "<html><body><h1>Minimalism!"
{:ok, filename} = PdfGenerator.generate html_works_too, generator: :chrome, prefer_system_executable: true

If using chrome in a superuser/root environment (read: docker), make sure to pass an option to chrome to disable sandboxing. And be aware of the implications.

html_works_too = "<html><body><h1>I need Docker, baby docker is what I need!"
{:ok, filename} = PdfGenerator.generate html_works_too, generator: :chrome, no_sandbox: true

Or use the bang-methods:

filename   = PdfGenerator.generate! "<html>..."
pdf_binary = PdfGenerator.generate_binary! "<html>..."

Options and Configuration

This module will automatically try to finde both wkhtmltopdf and pdftk in your path. But you may override or explicitly set their paths in your config/config.exs.

config :pdf_generator,
    wkhtml_path:    "/usr/bin/wkhtmltopdf",   # <-- this program actually does the heavy lifting
    pdftk_path:     "/usr/bin/pdftk"          # <-- only needed for PDF encryption

or, if you prefer chrome-headless

config :pdf_generator,
    use_chrome: true,                           # <-- make sure you installed node/puppeteer
    prefer_system_executable: true              # <-- set this if you installed the NPM dependencies globally
    raise_on_missing_wkhtmltopdf_binary: false, # <-- so the app won't complain about a missing wkhtmltopdf

More options

  • filename - filename for the output pdf file (without .pdf extension, defaults to a random string)

  • page_size:

    • defaults to A4, see wkhtmltopdf for more options
    • letter (for US letter) be translated to 8x11.5 inches (currently, only in chrome).

  • open_password: requires pdftk, set password to encrypt PDFs with

  • edit_password: requires pdftk, set password for edit permissions on PDF

  • shell_params: pass custom parameters to wkhtmltopdf. CAUTION: BEWARE OF SHELL INJECTIONS!

  • command_prefix: prefix wkhtmltopdf with some command or a command with options (e.g. xvfb-run -a, sudo ..)

  • delete_temporary: immediately remove temp files after generation

Contribution; how to run tests

You're more than welcome ot submit patches. Please run mix test to ensure at bit of stability. Tests require a full-fledged environment, with all of wkhtmltopdf, xvfb and chrome-headless-render-pdf available path. Also make to to have run npm install in the app's base directory (will install chrome-headless-render-pdf non-globally in there). With all these installed, mix test should run smoothly.

Hint: Getting :enoent errors ususally means that chrome or xvfb couldn't be run. Yes, this should output a nicer error.

Heroku Setup

If you want to use this project on heroku, you can use buildpacks instead of binaries to load pdftk and wkhtmltopdf:

https://github.com/fxtentacle/heroku-pdftk-buildpack
https://github.com/dscout/wkhtmltopdf-buildpack
https://github.com/HashNuke/heroku-buildpack-elixir
https://github.com/gjaldon/phoenix-static-buildpack

note: The list also includes Elixir and Phoenix buildpacks to show you that they must be placed after pdftk and wkhtmltopdf. It won't work if you load the Elixir and Phoenix buildpacks first.

Running non-patched wkhtmltopdf headless

This section only applies to wkhtmltopdf users using wkhtmltopdf w/o the qt patch. If you are using the latest 0.12 binaries from https://downloads.wkhtmltopdf.org (recommended) you can safely skip this section.

If you want to run wkhtmltopdf with an unpatched verison of webkit that requires an X Window server, but your server (or Mac) does not have one installed, you may find the command_prefix handy:

PdfGenerator.generate "<html..", command_prefix: "xvfb-run"

This can also be configured globally in your config/config.exs:

config :pdf_generator,
    command_prefix: "/usr/bin/xvfb-run"

If you will be generating multiple PDFs simultaneously, or in rapid succession, you will need to configure xvfb-run to search for a free X server number, or set the server number explicitly. You can use the command_prefix to pass options to the xvfb-run command.

config :pdf_generator,
    command_prefix: ["xvfb-run", "-a"]

Documentation

For more info, read the docs on hex or issue h PdfGenerator in your iex shell.

Known issues

Unfortunately, with Elixir 1.7+ System.cmd seems to pass parameters differently to the environment than it did before, now requiring shell options like --foo=bar to be split up as ["--foo", "bar"]. This behaviour seemingly went away with OTP 22 in May 2019 and Elixir 1.8.2. So if you run into issues, try upgrading to the latest Erlang/OTP and Elixir first, and do not hesitate file a report.

Contributing

Contributions (Issues, PRs…) are more than welcome. Please ave a quick read at the Contribution tips, though. It's basically about scope and kindness.

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A simple wrapper for wkhtmltopdf (HTML to PDF) for use in Elixir projects.

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