How-to-serve-dynamically-created-pdf.md

So, let's see how to use muhammara to build a PDF, and write it directly to the stream. The example shows basics of using Muhammara, creating a PDF stream, adding a page to it, and some text.

The full code listing is in here.

We'll start by creating a new script file, name it PDFServer.js.
use npm install to get express and Muhammara:

npm install express
npm install muhammara

Now let's write some basic server code using express. This parts is plain express, so just grab it as is:

var express = require("express");
var app = express();
app.get("/", function (req, res) {
  res.writeHead(200, { "Content-Type": "application/pdf" });

  /** here we will place the pdf building code **/

  res.end();
});
app.listen(3000);

This code simply creates a server that listens to port 3000. Note that the response content type is set to application/pdf so that the placed PDF content is interpreted as such.

Now, we'll write some PDF code. The following should be placed where the comment is.

start by fetching the muhammara module and create a PDF writer:

var muhammara = require("muhammara");
var pdfWriter = muhammara.createWriter(new muhammara.PDFStreamForResponse(res));

The code uses muhammara.createWriter method to create a PDF file writer. This method can receive either a string denoting a file path, or an object. The object, if provided, is a custom stream object. In this case it's an instance of PDFStreamForResponse class, which is an implementation of a custom stream writing to the server response object.

Next, we'll start a page:

var page = pdfWriter.createPage(0, 0, 595, 842);

Not much to say about this. using the writer to create an A4 sized page. Dimensions, as is the case for the whole module, as in points (1/72 of an inch, the basic PDF measurement unit).
There are 4 numbers (and not 2), cause we're providing the full media box of the page. It can be non-zero if you want margins.

Now, let's add some text:

pdfWriter
  .startPageContentContext(page)
  .writeText("Hello " + (req.query.id ? req.query.id : "World"), 0, 400, {
    font: pdfWriter.getFontForFile("./fonts/arial.ttf"),
    size: 50,
    colorspace: "gray",
    color: 0x00,
  });

k. quite a bit happens here, so let's explain slowly.
pdfWriter.startPageContentContext(page) creates a content context to the page, which is what you have to create in order to draw anything on top of it. This object has lot's of methods, allowing to add images, text, primitives, and use any of the PDF commands to draw anything. All it's methods are chain-able.

Then, its WriteText command is used to write some text. The first parameter is the text to write. In this case - 'Hello ' + (req.query.id ? req.query.id : 'World') - is simply Hello with the value of the url parameter id.
The 2nd and 3rd parameters are the X and Y coordinates in which to place the text.
The 4th object is a style descriptor, which holds the font info, the color and font size:

{
    font:pdfWriter.getFontForFile('./fonts/arial.ttf'),
    size:50,
    colorspace:'gray',
    color:0x00
}

The font entry uses pdfWriter.getFontForFile method to create a font object based on the font in the input path. In this case it's arial.ttf.
size is, well, size.
colorspace is the color space to use. There's gray, cmyk or rgb. Then comes color which has the color values written as a hex encoded color value. For each color component (number varying per the colorspace) there's a pair of hex values, from - 00 to FF. In this case it's 0x00 cause we want black. If it were an rgb color space we'll have something like 0xFE34DF, which means - 3 color components.

k. now let's just finish that Page, and the PDF with the following:

pdfWriter.writePage(page);
pdfWriter.end();

the writePage command finishes a page, which means you don't get to write to it after calling this. end will finish the PDF and make it available (it won't do much, just add the font definition, mainly).

Done. We got a dynamically created PDF served directly to the response. Neat.

Learn about more feature of the module in Features.