PDF Generator

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

See Changelog for recent changes.

Usage

Hint: In IEx, h PdfGenerator.generate is your friend.

For Elixir version earlier than 1.4:

def application do
    [
      applications: [
        :logger,
        :pdf_generator
      ]
    ]
end

Add this to your dependencies in your mix.exs:

defp deps do
[
  # ... whatever else
  {:pdf_generator, ">=0.6.0" }, # <-- and this
]
end

If you want to use a locally-installed chromium in RELEASES (think mix release), alter your mixfile to let make take care of compilation and dependency-fetching:

defp deps do
  [
    {:pdf_generator, ">=0.6.2", compile: "make chrome"}
  ]
end

To get the latest version or if you run into issues:

defp deps do
  [
    {:pdf_generator, "~> 0.6.2", github: "gutschilla/elixir-pdf-generator", compile: "make chrome"}
  ]
end

This will embed a 300 MB (yes, that large) Chromium binary into your priv folder which will survive packaging as Erlang release. This can be handy as this will run on slim Alpine docker images with just NodeJS installed.

The recommended way still is to install Chromium/Puppeteer globally and set the prefer_system_executable: true option when generating PDFs.

In development: While this usually works, it unfortunately leads to pdf_generator to be compiled all the time again and again due to my bad Makefile skills. Help is very much appreciated.

Eventually, if you are using Phoenix and you would like to have your npm packages installed locally, within the /assets/node_modules directory, simply run npm install chrome-headless-render-pdf puppeteer within assets/node_modules and pass prefer_local_executable: true option when generating the PDF like this:

PdfGenerator.generate(url, generator: :chrome, prefer_local_executable: true)

Try it out

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 the bang-methods:

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

Chrome

Or, use chrome-headless.

Unless your mixfile says {:pdf_generator, ">=6.0.0", compile: "make chrome"} Chrome won't be installed into your application. Please set the prefer_system_executable: true option in this case.

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

Docker

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, page_size: "letter"

System prerequisites

It's either

wkhtmltopdf or
NodeJS (for Chrome-headless/Puppeteer)

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.

Global Install (great for Docker images)

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, use the compile: "make chrome" option in your mixfile's dependency-line.

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

Local Install

Run make priv/node_modules. This requires both nodejs (installation see above) and make.

Or, run cd priv && npm install

wkhtmltopdf

Alpine (tested on 3.11): apk add wkhtmltopdf - gone are the days of manually fumbling around with wkhtmltopdf and its muss preference over glibc.
Ubuntu 19.10+: apt-get install wkhtmltopdf and you'll have 0.12.5 on $PATH
Ubuntu 18.04: 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

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

To use other wkhtmltopdf executables compiled 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 am glad to have received feedback that people are actually using this feature.
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

Options and Configuration

This module will automatically try to find 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 or chrome-headless-render-pdf. 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

You're more than welcome to 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 usually 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 version 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.generate 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 have a quick read at the Contribution tips, though. It's basically about scope and kindness.

Copyright and License

Released under the MIT License, which can be found in LICENSE.md.

gutschilla/elixir-pdf-generator

gutschilla

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