Creating a PDF Document from Scratch

In this tutorial you will create a simple PDF document from scratch with HexaPDF. It only assumes that you have the Ruby interpreter already installed.

Installing HexaPDF

The first step is installing HexaPDF itself as a Rubygem:

$ gem install hexapdf

This will install HexaPDF as well as its dependencies. Afterwards the HexaPDF library and the hexapdf command line tool are available.

Requiring HexaPDF

If you want to use HexaPDF in a Ruby program, you need to include the following statement:

require 'hexapdf'

This will only require the base HexaPDF library parts but also sets everything up so that all functionality will be auto-loaded if needed.

Creating the PDF Document

To create a PDF document you will first need an empty document instance:

doc = HexaPDF::Document.new

Now that you have that empty document, let’s add a page:

page = doc.pages.add

In this simplest form an empty A4-sized page is created. Once the page is available, you can use HexaPDF’s drawing API to put something on it. To access the drawing API you need the canvas:

canvas = page.canvas

The canvas provides many methods for drawing lines, rectangles, curves, text, … and for changing drawing aspects like the stroke color. For now, you will just draw the text “Hello World” on it. Set the font and font size as well as the fill color like this:

canvas.font('Helvetica', size: 50).
  fill_color(0, 128, 255)

Setting the stroke color can be done in various ways, here an RGB (red, green, blue) value is used.

Before drawing the text onto the canvas you need to know two things:

  1. The coordinate system of a PDF page has its origin at the lower-left corner, positivie x-axis is to the right, positive y-axis up, so just like the mathematical notation of the 2D space.

  2. Coordinates are specified in PDF points where 72 PDF points are one inch.

Now you can draw the text in roughly the center of the page (A4 is 595x842 points):

canvas.text("Hello World", at: [150, 396])

The page has some contents now; the last thing to do is to write the PDF document to a file:

doc.write("hello-world.pdf")

Save the code and run it. It will create the hello-world.pdf file with the “Hello World” page in it! If you followed the tutorial without having access to a computer, you can also view the PDF file here.

You might wanna play around a bit with different HexaPDF::Content::Canvas methods, for example, to draw lines or bezier curvers with different line width and colors.

When you are ready, head on to the next tutorial about modifying a PDF document.

The Complete Code and Result PDF

Here is the complete code generating this result PDF:

require 'hexapdf'

doc = HexaPDF::Document.new

page = doc.pages.add

canvas = page.canvas

canvas.font('Helvetica', size: 50).
  fill_color(0, 128, 255)

canvas.text("Hello World", at: [150, 396])

doc.write("hello-world.pdf")