wkhtmltopdf
Vapor 4 library for converting HTML (Leaf or otherwise) into PDF files using wkhtmltopdf.
Getting Started
Add the following in your Package.swift file
.package(url: "https://github.com/vapor-community/wkhtmltopdf.git", from: "4.0.0"),📘 Overview
First, install wkhtmltopdf. This
library is tested on version 0.12.5. Specify the location of wkhtmltopdf
in the Document initialiser. The default is /usr/local/bin/wkhtmltopdf.
Run it to ensure it and any dependencies are installed correctly.
To create a PDF, create and configure a Document, add one or more Pages,
and then call generatePDF(on: threadPool, eventLoop: eventLoop). Here is a full example using Vapor:
import wkhtmltopdf
func pdf(_ req: Request) -> EventLoopFuture<Response> {
// Create document. Margins in mm, can be set individually or all at once.
// If no margins are set, the default is 20mm.
let document = Document(margins: 15)
// Create a page from an HTML string.
let page1 = Page("<p>Page from direct HTML</p>")
// Create a page from a Leaf template.
let page2 = req.view.render("page_from_leaf_template")
// Create a page from a Leaf template with Context variables.
let context = ["firstName": "Peter", "lastName": "Pan"]
let page3 = req.view.render("page_from_leaf_template", context)
let pages = [ page2, page3]
.flatten(on: req.eventLoop)
.map { views in
views.map { Page($0.data) }
}
return pages.flatMap { pages in
// Add the pages to the document
document.pages = [page1] + pages
// Render to a PDF
let pdf = document.generatePDF(on: req.application.threadPool, eventLoop: req.eventLoop)
// Now you can return the PDF as a response, if you want
return pdf.map { data in
return Response(
status: .ok,
headers: HTTPHeaders([("Content-Type", "application/pdf")]),
body: .init(data: data)
)
}
}
}In your Leaf file, you may want to load resources such as images, CSS
stylesheets and web fonts. Store these in your Public directory, and you can
direct wkhtmltopdf to this directory using the #(publicDir) tag.
If you'd like to use a non-public directory, you can use the #(workDir) tag
to render the Droplet's working directory. Of course, you can always hard-code
an absolute path instead.
Here is a worked example Leaf file which loads CSS and images. It uses the
<base> tag to tell wkhtmltopdf to look in the Public directory by default.
<!DOCTYPE html>
<html>
<head>
<base href='#(publicDir)'>
<link href='css/pdf.css' rel='stylesheet'>
</head>
<body>
<img src='img/welcome.jpg'>
<p>Welcome #(firstName) #(lastName)!</p>
</body>
</html>Zoom calibration
Across different platforms, wkhtmltopdf can require different zoom levels to
ensure that 1 mm in HTML equals 1 mm in PDF. The default zoom level is 1.3,
which has been found to work well on Linux, but if you need a different zoom
level set the static property Document.zoom before doing any rendering.
Why Pages?
WebKit is not very good at rendering page breaks. If it works with your design,
a good alternative is to split the PDF document into separate HTML files.
wkhtmltopdf will combine them all and return a single PDF document.