kitabu

Kitabu is a framework for creating e-books from Markdown using Ruby. Using Prince PDF generator, you'll be able to get high quality PDFs. Also supports EPUB, Mobi, and HTML generation.

While Prince is too expensive (495USD for a single user license), the free version available at http://www.princexml.com/download generates a PDF with a small logo on the first page, which is removed when sent to a printer; you can use it locally for viewing the results immediately. When you're done writing your e-book, you can use DocRaptor, which have plans starting at $15/mo.

Features

• Write using Markdown
• Book layout support
• Syntax highlight
• Generate HTML, PDF, e-Pub (version 3.3), and Mobi
• Table of Contents automatically generated from chapter titles

Installation

To install Kitabu, you'll need a working Ruby 3.2+ installation. If you're cool with it, just run the following command to install it.

gem install kitabu

After installing Kitabu, run the following command to check your external dependencies.

$ kitabu check

Prince XML: Converts HTML files into PDF files.
Installed.

Calibre's ebook-convert: Converts ePub e-books into .mobi files.
Installed.

There are no hard requirements here; just make sure you cleared the correct dependency based on the formats you want to export to.

Usage

To create a new e-book, just run

$ kitabu new mybook

This command creates a directory mybook with the following structure:

.
├── Gemfile
├── Gemfile.lock
├── Guardfile
├── assets
│   ├── fonts
│   ├── images
│   │   ├── cover.png
│   │   ├── kitabu.svg
│   │   ├── markdown.svg
│   │   └── up.svg
│   ├── scripts
│   └── styles
│       ├── epub.css
│       ├── html.css
│       ├── pdf.css
│       ├── print.css
│       └── support
│           ├── kitabu.css
│           ├── normalize.css
│           ├── notes.css
│           └── toc.css
├── config
│   ├── helpers.rb
│   ├── kitabu.yml
│   └── locales
│       └── en.yml
├── templates
│   ├── epub
│   │   ├── cover.erb
│   │   ├── page.erb
│   │   └── toc.erb
│   └── html
│       └── layout.erb
└── text
    ├── 01_Getting_Started.md
    ├── 02_Creating_Chapters.md
    ├── 03_Syntax_Highlighting.md.erb
    ├── 04_Dynamic_Content.md.erb
    ├── 05_Exporting_Files.md
    └── 06_Changelog.md

13 directories, 28 files

The config/kitabu.yml file holds some information about your book; so you'll always change it.

The generated structure is actually a good example. So make sure you try it!

There's a generated sample available on the attachments directory • PDF / EPUB / MOBI / HTML.

Now it's time to write your e-book. All your book content will be placed on the text directory. Kitabu requires you to separate your book into chapters. A chapter is nothing but a directory that holds lots of text files. The e-book will be generated using every folder/file alphabetically. So be sure to use a sequential numbering as the name. Here's a sample:

* text
  * 01_Introduction
    * 01_introduction.md
  * 02_What_is_Ruby_on_Rails
    * 01_MVC.md
    * 02_DRY.md
    * 03_Convention_Over_Configuration.md
  * 03_Installing_Ruby_on_Rails
    * 01_Installing.md
    * 02_Mac_OS_X_instructions.md
    * 03_Windows_instructions.md
    * 04_Ubuntu_Linux_instructions.md

If you prefer, you can add a chapter per file:

* text
  * 01_Introduction.md
  * 02_What_is_Ruby_on_Rails.md
  * 03_Installing_Ruby_on_Rails.md

You'll want to see your progress eventually; it's time for you to generate the book PDF. Just run the command kitabu export and your book will be created on the output directory.

Kitabu can generate a Table of Contents (TOC) based on your h1-h6 tags. To print the TOC, you need to print a variable called toc, using the eRb tag.

<%= toc %>

Frontmatter

Markdown files (and their .md.erb counterparts) support frontmatter, a section that can inject variables to the page. Notice that the contents inside the --- delimiters must be valid YAML annotation and only basic types can be used (booleans, numbers, strings, nils and hashes/arrays with these same types).

Right now there's only one special value called section, which defines the class section when generating files. This allows you to have files inside your text directory that doesn't necessarily should have styling like regular chapters. For instance, this is how you can define a changelog section:

---
section: changelog
---

## Changelog

### Jan 26, 2024

- Initial release

[!NOTE]

Notice that section will be retrieved from the first file, even if you have multiple files defining a section with a directory.

This meta data will be inject on your template using the variable meta. If you have other variables, you could print them as <%= meta["varname"] %>.

Using ERB

You can also have .md.erb files. You can mix Markdown and HTML, like the following:

## This the chapter title

<%= image_tag "myimage.png" %>

The above content must be placed in a .md.erb file. The generated content will be something like this:

<img src="images/myimage.png" />

You book's helpers can be added to config/helpers.rb, as this file is loaded automatically by kitabu.

You can see available helpers on https://github.com/fnando/kitabu/blob/main/lib/kitabu/helpers.rb.

Syntax Highlighting

To highlight code, use fenced code blocks.

``` ruby
class User < ActiveRecord::Base
  validates_presence_of :login, :password, :email
  validates_uniqueness_of :login, :email
end
```

You can even provide options:

```php?start_line=1&line_numbers=1
echo "Hello World";
```

• We use Redcarpet for Markdown processing.
• We use Rouge for syntax highlighting.

The following Redcarpet options are enabled:

• autolink
• fenced_code_blocks
• footnotes
• hard_wrap
• highlight
• no_intra_emphasis
• safe_links_only
• space_after_headers
• strikethrough
• superscript
• tables

Hooks

There are a few hooks that allows manipulating the content. You can use before_render and after_render to process the Markdown content. You can add such hooks to your config/helpers.rb file.

Kitabu::Markdown.add_hook(:before_render) do |content|
  # manipulate content and return it.
  content
end

Kitabu::Markdown.add_hook(:after_render) do |content|
  # manipulate content and return it.
  content
end

Using custom fonts

You can use custom fonts on your ebooks. Just add them to the fonts directory (you can create this directory on your book's root directory if it doesn't exist).

Then, on assets/styles/support/fonts.css you can add the @font-face declaration.

@font-face {
  font-family: "Open Sans Condensed Bold";
  src: url("../../fonts/OpenSans-CondBold.ttf");
}

Finally, to use this font, do something like this:

.chapter > h1 {
  font-family: "Open Sans Condensed Bold";
}

Instead of doing the above manually, you can also use Prince's --scanfonts option.

$ prince --scanfonts assets/fonts/* > assets/styles/support/fonts.css

Just remember to replace the generated path to be something like ../../fonts instead.

[!TIP]

In most cases, it's easier to redefine sans-serif, serif and monospace fonts. To know more about how to do this, read Prince's Redefining the generic font families documentation.

If you're unsure if fonts are actually being used on PDF files, use the environment variable PRINCEOPT to disable system fonts.

$ PRINCEOPT='--no-system-fonts --debug --log output/prince.log' kitabu export --only pdf
=> e-book couldn't be exported

$ tail -n10 output/prince.log
Sat Jan 27 18:39:10 2024: debug: font request: Caslon, serif
Sat Jan 27 18:39:10 2024: warning: Ensure fonts are available on the system or load them via a @font-face rule.
Sat Jan 27 18:39:10 2024: warning: For more information see:
Sat Jan 27 18:39:10 2024: warning: https://www.princexml.com/doc/help-install/#missing-glyphs-or-fonts
Sat Jan 27 18:39:10 2024: internal error: Unable to find any available fonts.
Sat Jan 27 18:39:10 2024: finished: failure
Sat Jan 27 18:39:10 2024: ---- end

Configuring Markdown

Kitabu uses Redcarpet as the Markdown engine. You can override the default processor by setting Kitabu::Markdown.processor. This can be done by adding something like the following to config/helpers.rb:

Kitabu::Markdown.processor = Redcarpet::Markdown.new(
  Kitabu::Markdown::Renderer.new(hard_wrap: false, safe_links_only: true),
  tables: true,
  footnotes: true,
  space_after_headers: true,
  superscript: true,
  highlight: true,
  strikethrough: true,
  autolink: true,
  fenced_code_blocks: true,
  no_intra_emphasis: true
)

The above options are Kitabu's defaults.

Exporting PDFs using DocRaptor

If you're not planning to