html3pdf

html3pdf

html3pdf converts any webpage or element into a printable PDF entirely client-side using html2canvas and jsPDF.

This library is a continuation of, and is compatible with the API for, html2pdf.js by Erik Koopmans. The majority of this README was written by Erik Koopmans.

Differences from html2pdf.js:

Breaking changes:

• Dropped support for environments that don't have native Promises.
• Previously if you called the .toPdf() method of the html2pdf.js object, without explicitly calling .toCanvas() or .toImg(), the default worker object would have the properties .prop.canvas and .prop.img, which would be an HTMLCanvasElement and an HTMLImageElement respectively. Now the default types are Array<HTMLCanvasElement> and Array<HTMLImageElement>. If you do not want them to be arrays, you can explicitly call .toCanvas() and .toImg(). See Workflow below for more details. This is a niche use case and if you don't know what any of this means, you probably don't need to worry about it.

Features/Bug fixes:

• Progress tracking API implemented.
• .toCanvases() and .toImgs() added to the worker API as alternatives to the original .toCanvas() and .toImg() methods. These are now the default if you simply call .toPdf() without being explicit about the rest of the chain. These functions create one canvas per page, and the corresponding images for each canvas. This resolves the issues with canvas size limits (unless each page is enormous).
• PRs from the original library merged: 170, 260, 261, 340, 447, 503, 516, 531, 569, 635, 641. These include: some fixes to the pagebreak calculations, the option to change what elements are used for pagebreaks and assign a class to those elements, the addition of the jsPDF documentProperties to the api, and a fix for the bug where long documents are blank - by rendering one canvas per page.

Table of contents

• Getting started
  • CDN
  • Raw JS
  • NPM
  • Bower
  • Console
• Usage
  • Advanced usage
    • Workflow
    • Worker API
• Options
  • Page-breaks
    • Page-break settings
    • Page-break modes
    • Example usage
  • Image type and quality
• Progress tracking
• Dependencies
• Contributing
  • Issues
  • Tests
  • Pull requests
• Credits
• License

Getting started

CDN

The simplest way to use html3pdf is to include it as a script in your HTML by using cdnjs:

<script src="" integrity="" crossorigin="anonymous" referrerpolicy="no-referrer"></script>

// TODO - add to CDN and add link here

Note: Read about dependencies for more information about using the unbundled version dist/html2canvas.min.js.

Raw JS

You may also download dist/html3pdf.bundle.min.js directly to your project folder and include it in your HTML with:

<script src="html3pdf.bundle.min.js"></script>

NPM

Install html3pdf and its dependencies using NPM with npm install --save html3pdf

Note: You can use NPM to create your project, but html3pdf will not run in Node.js, it must be run in a browser.

Console

If you're on a webpage that you can't modify directly and wish to use html3pdf to capture a screenshot, you can follow these steps:

1. Open your browser's console (instructions for different browsers here).
2. Paste in this code:

   function addScript(url) {
       const script = document.createElement('script');
       script.type = 'application/javascript';
       script.src = url;
       document.head.appendChild(script);
   }
   addScript('');  // TODO add cdn link here
   

3. You may now execute html3pdf commands directly from the console. To capture a default PDF of the entire page, use html2pdf(document.body).

Usage

Once installed, html3pdf is ready to use. The following command will generate a PDF of #element-to-print and prompt the user to save the result:

const element = document.getElementById('element-to-print');
html2pdf(element);

Advanced usage

Every step of html3pdf is configurable, using a Promise-based API. If html3pdf is called without arguments, it will return a Worker object:

const worker = html2pdf();  // Or:  const worker = new html2pdf.Worker;

This worker has methods that can be chained sequentially, as each Promise resolves, and allows insertion of your own intermediate functions between steps. A prerequisite system allows you to skip over mandatory steps (like canvas creation) without any trouble:

// This will implicitly create the canvases and PDF objects before saving.
const worker = html2pdf().from(element).save();

Workflow

The basic workflow of html3pdf tasks (enforced by the prereq system) is:

// The default in html3pdf
.from() -> .toContainer() -> .toCanvases() -> .toImgs() -> .toPdf() -> .save()

// The default in html2pdf.js
.from() -> .toContainer() -> .toCanvas() -> .toImg() -> .toPdf() -> .save()

// You can also call .toImgs() after calling toCanvas(), it will just have an array with one image.
.from() -> .toContainer() -> .toCanvas() -> .toImgs() -> .toPdf() -> .save()

// But you can't call `.toImg` if you previously called `.toCanvases` on the same worker, `.toImg` does not want to assemble a single image out of multiple canvases.  If you need this for some reason, feel free to submit a PR!

Worker API

Method	Arguments	Description
from	src, type	Sets the source (HTML string or element) for the PDF. Optional type specifies other sources: 'string', 'element', 'canvas', or 'img'.
to	target	Converts the source to the specified target ('container', 'canvas', 'canvases', 'img', 'imgs', or 'pdf'). Each target also has its own toX method that can be called directly: toContainer(), toCanvas(), toCanvases(), toImg(), toImgs(), and toPdf().
output	type, options, src	Routes to the appropriate outputPdf or outputImg method based on specified src ('pdf' (default) or 'img').
outputPdf	type, options	Sends type and options to the jsPDF object's output method, and returns the result as a Promise (use .then to access). See the jsPDF documentation for more info.
outputImg	type, options	Returns the specified data type for the image as a Promise (use .then to access). Supported types: 'img', 'datauristring'/'dataurlstring', and 'datauri'/'dataurl'.
save	filename, documentProperties	Saves the PDF object (creates user download prompt) with the optional filename and document properties (see jsPDF DocumentProperties). Ex. html2pdf().save('output.pdf', { title: 'My PDF' })
set	opt	Sets the specified properties. See Options below for more details.
get	key, cbk	Returns the property specified in key, either as a Promise (use .then to access), or by calling cbk if provided.
then	onFulfilled, onRejected	Standard Promise method, with this re-bound to the Worker, and with added progress-tracking (see Progress below). Note that .then returns a Worker, which is a subclass of Promise.
thenCore	onFulFilled, onRejected	Standard Promise method, with this re-bound to the Worker (no progress-tracking). Note that .thenCore returns a Worker, which is a subclass of Promise.
thenExternal	onFulfilled, onRejected	True Promise method. Using this 'exits' the Worker chain - you will not be able to continue chaining Worker methods after .thenExternal.
catch, catchExternal	onRejected	Standard Promise method. catchExternal exits the Worker chain - you will not be able to continue chaining Worker methods after .catchExternal.
error	msg	Throws an error in the Worker's Promise chain.
listen	(progress) => void	Lets you pass a callback that will be called after each step of the html2pdf process completes. Useful for making progress bars, etc.

A few aliases are also provided for convenience:

Method	Alias
save	saveAs
set	using
output	export
then	run

Options

html3pdf can be configured using an optional opt parameter:

const element = document.getElementById('element-to-print');
const opt = {
  margin:             1,
  filename:           'myFile.pdf',
  image:              { type: 'jpeg', quality: 0.98 },
  html2canvas:        { scale: 2 },
  jsPDF:              { unit: 'in', format: 'letter', orientation: 'portrait' }
  documentProperties: { title: 'My PDF' }
};

// New Promise-based usage:
html2pdf().set(opt).from(element).save();

// Old monolithic-style usage:
html2pdf(element, opt);

The opt parameter has the following optional fields:

Name	Type	Default	Description
margin	number or array	0	PDF margin (in jsPDF units). Can be a single number, [vMargin, hMargin], or [top, left, bottom, right].
filename	string	'file.pdf'	The default filename of the exported PDF.
pagebreak	object	{mode: ['css', 'legacy']}	Controls the pagebreak behaviour on the page. See Page-breaks below.
image	object	{type: 'jpeg', quality: 0.95}	The image type and quality used to generate the PDF. See Image type and quality below.
enableLinks	boolean	true	If enabled, PDF hyperlinks are automatically added on top of all anchor tags.
html2canvas	object	{ }	Configuration options sent directly to html2canvas (see here for usage).
jsPDF	object	{ }	Configuration options sent directly to jsPDF (see here for usage).
documentProperties	object	{ }	Configuration options applied directly to jsPDF pdf (see here for usage).

Page-breaks

html3pdf has the ability to automatically add page-breaks to clean up your document. Page-breaks can be added by CSS styles, set on individual elements using selectors, or avoided from breaking inside all elements (avoid-all mode).

By default, html3pdf will respect most CSS break-before, break-after, and break-inside rules, and also add page-breaks after any element with class html2pdf__page-break (for legacy purposes).

Page-break settings

Setting	Type	Default	Description
mode	string or array	['css', 'legacy']	The mode(s) on which to automatically add page-breaks. One or more of 'avoid-all', 'css', and 'legacy'.
before	string or array	[]	CSS selectors for which to add page-breaks before each element. Can be a specific element with an ID ('#myID'), all elements of a type (e.g. 'img'), all of a class ('.myClass'), or even '*' to match every element.
after	string or array	[]	Like 'before', but adds a page-break immediately after the element.
avoid	string or array	[]	Like 'before', but avoids page-breaks on these elements. You can enable this feature on every element using the 'avoid-all' mode.

Page-break modes

Mode	Description
avoid-all	Automatically adds page-breaks to avoid splitting any elements across pages.
css	Adds page-breaks according to the CSS break-before, break-after, and break-inside properties. Only recognizes always/left/right for before/after, and avoid for inside.
legacy	Adds page-breaks after elements with class html2pdf__page-break. This feature may be removed in the future.

Example usage

// Avoid page-breaks on all elements, and add one before #page2el.
html2pdf().set({
  pagebreak: { mode: 'avoid-all', before: '#page2el' }
});

// Enable all 'modes', with no explicit elements.
html2pdf().set({
  pagebreak: { mode: ['avoid-all', 'css', 'legacy'], elementType: 'div', className: 'page_break' }  // you can change what kind of element is injected as a pagebreak, and add a class name to style those elements
});

// No modes, only explicit elements.
html2pdf().set({
  pagebreak: { before: '.beforeClass', after: ['#after1', '#after2'], avoid: 'img' }
});

Image type and quality

You may customize the image type and quality exported from the canvas by setting the image option. This must be an object with the following fields:

Name	Type	Default	Description
type	string	'jpeg'	The image type. HTMLCanvasElement only supports 'png', 'jpeg', and 'webp' (on Chrome).
quality	number	0.95	The image quality, from 0 to 1. This setting is only used for jpeg/webp (not png).

These options are limited to the available settings for HTMLCanvasElement.toDataURL(), which ignores quality settings for 'png' images. To enable png image compression, try using the canvas-png-compression shim, which should be an in-place solution to enable png compression via the quality option.

Progress tracking

The Worker object returned by html2pdf() has a built-in progress-tracking mechanism. Call the .listen() method at the end of your chain, e.g:

html2pdf().set(opt).from(element).save().listen(progressCallback);

The progressCallback should be a void function that accepts a single argument, which is this object:

 {
  val:    number   -  The current progress step.
  state:  string   -  A string describing the current step.
  n:      number   -  The number of total steps that will be completed.
  stack:  string[] -  The current stack of functions to be executed.
  ratio:  number   -  The current progress ratio. (val/n) -> Use this for progress bars!
 }

Dependencies

html3pdf depends on the external packages html2canvas, and jsPDF). These dependencies are automatically loaded when using NPM or the bundled package.

If using the unbundled dist/html3pdf.min.js (or its un-minified version), you must also include each dependency. Order is important, otherwise html2canvas will be overridden by jsPDF's own internal implementation:

<script src="jspdf.min.js"></script>
<script src="html3canvas.min.js"></script>
<script src="html3pdf.min.js"></script>

Contributing

Issues

When submitting an issue, please remember that html3pdf is a wrapper around html2canvas and jsPDF, so it's a good idea to check each of those repositories' issue trackers to see if your problem has already been addressed.

Known issues

1. Rendering: The rendering engine html2canvas isn't perfect (though it's pretty good!). If html2canvas isn't rendering your content correctly, we can't fix it.

2. Node cloning (CSS etc): The way html3pdf clones your content before sending to html2canvas is buggy. A fix was being developed in html2pdf.js

3. Resizing: Currently, html3pdf resizes the root element to fit onto a PDF page (causing internal content to "reflow"). This is often desired behaviour, but not always.

4. Rendered as image: html3pdf renders all content into an image, then places that image into a PDF. This means text is not selectable or searchable, and causes large file sizes. This is the unavoidable reality of the html3pdf system of using html2canvas to render everything first. jsPDF may be used as the renderer in the future to avoid this.

Tests

Any contributions or suggestions of automated (or manual) tests are welcome. This is high on the to-do list for this project.

Pull requests

If you want to create a new feature or bugfix, please feel free to fork and submit a pull request! Create a fork, branch off of master, and make changes to the /src/ files (rather than directly to /dist/). You can test your changes by rebuilding with npm run build.

Credits

Erik Koopmans, html2pdf.js, and all other contributors to that project!

License

The MIT License

Copyright (c) 2017-2019 Erik Koopmans <http://www.erik-koopmans.com/>