Golang : Create PDF file from HTML file

When I was coding with PHP and CodeIgniter framework, I need to generate PDF file to email receipts to my customers. In CodeIgniter/PHP world, there are multiple third party library - such as DOMPDF - that can render and convert a HTML file to PDF file with ease.

In Golang world, one can try to utilise the GoPDF packages (https://github.com/signintech/gopdf) or another different GoPDF package (bitbucket.org/zombiezen/gopdf/pdf) . However, I found them complicated for my own use and unable to render HTML codes.

In this example, I will use os.Exec() function to render HTML file and generate PDF file with domPDF.

First, you need to download the domPDF package from https://github.com/dompdf/dompdf/downloads, unzip, set the right permission to execute dompdf.php file.

Second, you need to have PHP installed on the server you are executing this code. See https://code.google.com/p/dompdf/wiki/Installation on how to get domPHP installed properly.

Here you go :

 package main

 import (
 "bytes"
 "fmt"
 "io/ioutil"
 "net/http"
 "os"
 "os/exec"
 "path/filepath"
 )

 func Home(w http.ResponseWriter, r *http.Request) {
 w.Write([]byte(fmt.Sprintf("<html><body><form action='http://localhost:8080/pdf' method='post'><input type='submit' value='Generate PDF'></form></body></html>")))
 }

 func PDF(w http.ResponseWriter, r *http.Request) {

 // NOTE : receipt.html is a template file
 // for the sake of this tutorial, we are keeping things simple

 // use os.Exec to execute domPDF
 // read
 // https://code.google.com/p/dompdf/wiki/Usage#Invoking_dompdf_via_the_command_line
 // on how to configure and use domPDF from command line

 // change the sweetlogic path to yours !!

 // without filepath.Abs...it won't work! why???!?!
 arg1, _ := filepath.Abs("/Users/sweetlogic/dompdf/dompdf.php")
 arg2, _ := filepath.Abs("/Users/sweetlogic/receipt.html")



 cmd := exec.Command("php", arg1, arg2)
 out, err := cmd.Output()

 if err != nil {
 fmt.Println(string(out))
 fmt.Println(err)
 return
 }

 fmt.Print(string(out))

 // NOTE : In real world application, the output filename should be dynamic
 // and not static like in this example. For the sake of simplicity, we just
 // keep the output name to receipt.pdf
 // to change the output filename, see the domPDF command line instruction.

 // grab the generated receipt.pdf file and stream it to browser
 streamPDFbytes, err := ioutil.ReadFile("./receipt.pdf")

 if err != nil {
 fmt.Println(err)
 os.Exit(1)
 }

 b := bytes.NewBuffer(streamPDFbytes)

 // stream straight to client(browser)
 w.Header().Set("Content-type", "application/pdf")

 if _, err := b.WriteTo(w); err != nil {
 fmt.Fprintf(w, "%s", err)
 }

 w.Write([]byte("PDF Generated"))
 }

 func main() {
 // http.Handler
 mux := http.NewServeMux()
 mux.HandleFunc("/", Home)
 mux.HandleFunc("/pdf", PDF)

 http.ListenAndServe(":8080", mux)
 }

the content of the receipt.html file -- ripped off from one of my old project.

 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
 <html xmlns="http://www.w3.org/1999/xhtml">
 <head>
 <title><?php echo $title;?></title>
 <meta http-equiv="Content-Type" content="text/html;charset=utf-8" />
 <style type="text/css">
 /**
  * NOTE : This file NEEDS a locally located stylesheet to generate the appropriate formatting for
  * transformation into a PDF.  If you alter this file (and you are encouraged to do so) just
  * keep in mind that all of your formatting must be located here.  You might also find that
  * there is limited or no support for a specific CSS style you want (ie: floating) and you'll
  * need to work around with old-school tables.  Sorry for that... ;)
  *
  *
  * NOTE : Things have changed since I used domPDF with PHP. See latest updates on how
  * domPDF renders CSS at https://github.com/zimmski/dompdf
  *
  * - SocketLoop.com - Adam
  */


 body {
 width: 100%;
 margin: 0.5in;
 }

 h1, h2, h3, h4, h5, h6, li, blockquote, p, th, td {
 font-family: Helvetica, Arial, Verdana, sans-serif; /*Trebuchet MS,*/
 }
 h1, h2, h3 {
 color: #5E88B6;
 font-weight: normal;
 }
 h4, h5, h6 {
 color: #000;
 font-size:12px;
 }
 h2 {
 margin: 0 auto auto auto;
 font-size: x-large;
 }
 h2 span {
 text-transform: uppercase;
 }

 li, blockquote, p, th, td {
 font-size: 80%;
 }
 ul {
 list-style: url('../images/system/bullet.gif') none;
 }
 table {
 width: 100%;
 }

 td {
 padding: 7px 15px;
 }
 td p {
 font-size: small;
 margin: 0;
 }

 td h1 {
 font-size:36px;
 font-weight:bold;
 margin: 0;
 }

 thead, tfoot { background-color:black;color:white}

 th {
 color: #FFF;
 text-align: left;
 background-color:#000000;

 }
 .invoice_words {
 color: #000;
 font-size:22px;
 font-weight: bold;
 text-align: left;
 text-transform:uppercase;
 }
 .invoice_total {
 color: #000;
 font-size:12px;
 font-weight: bold;
 text-align: right;
 text-transform:uppercase;
 }

 #footer {
 border-top: 1px solid #CCC;
 text-align: right;
 font-size: 16px;
 color: #999999;
 }
 #footer a {
 color: #999999;
 text-decoration: none;
 }
 table.stripe {
 border-collapse: collapse;
 page-break-after: auto;
 }
 table.stripe td {
 border-bottom: 1pt solid black;
 }
 </style>
 </head>
 <body>

 <table>
 <tr>
 <td width="60%">
 <h1>
 <img src="https://d1ohg4ss876yi2.cloudfront.net/preview/golang.png"/>
 Receipt<br />
 </h1>
 <br />
 </td>
 <td>
 <h2>
 [company name]<br />
 </h2>
 <p>
 [your street address]<br/>
 Email: [your email address]<br />
 </p>
 </td>
 </tr>
 </table>

 <h3> You can add more data here or modify the CSS.... use your imagination! </h3>

 </body>
 </html>

now, run the code and point your browser to http://localhost:8080 and you should see a button to generate PDF. Click on the button and if everything goes smoothly, you should see a PDF file being downloaded.

Hope this tutorial is useful to you. Not entirely a 'pure' Golang tutorial because it relies on PHP packages.....but hey... it works.

NOTE : This is the bitbucket.org/zombiezen/gopdf/pdf code example I that I've tried, but not useful for me. Maybe it can be useful to you

 package main

 import (
 "bitbucket.org/zombiezen/gopdf/pdf"
 "fmt"
 "net/http"
 "os"
 )

 func Home(w http.ResponseWriter, r *http.Request) {
 w.Write([]byte(fmt.Sprintf("<html><body><form action='http://localhost:8080/pdf' method='post'><input type='submit' value='Generate PDF'></form></body></html>")))
 }

 func PDF(w http.ResponseWriter, r *http.Request) {
 doc := pdf.New()
 canvas := doc.NewPage(pdf.A4Width, pdf.A4Height)

 canvas.Translate(100, 100)

 path := new(pdf.Path)
 path.Move(pdf.Point{0, 0})
 path.Line(pdf.Point{100, 0})
 canvas.Stroke(path)

 text := new(pdf.Text)
 text.SetFont(pdf.Helvetica, 14)
 text.Text("Hello, World!")
 canvas.DrawText(text)


 text2 := new(pdf.Text)
 //text.SetFont(pdf.Helvetica, 14)

 html := "<html><body><h1>Receipt #0001</h2><br><br><h2>Issue to You!</h2></body></html>"

 text2.Text(html) // will not render ya
 canvas.DrawText(text2)

 canvas.Close()

 // download straight to browser
 w.Header().Set("Content-type", "application/pdf")
 err := doc.Encode(w)
 if err != nil {
 fmt.Println(err)
 os.Exit(1)
 }

 // save a copy on web server
 pdfFile, err := os.Create("x.pdf")

 if err != nil {
 fmt.Println(err)
 os.Exit(1)
 }

 doc.Encode(pdfFile)

 fmt.Println("Save to x.pdf...")

 w.Write([]byte("PDF Generated"))
 }

 func main() {
 // http.Handler
 mux := http.NewServeMux()
 mux.HandleFunc("/", Home)
 mux.HandleFunc("/pdf", PDF)

 http.ListenAndServe(":8080", mux)
 }

References :

https://godoc.org/bitbucket.org/zombiezen/gopdf/pdf

https://github.com/signintech/gopdf

https://github.com/dompdf/dompdf

Golang : Create PDF file from HTML file

By Adam Ng

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