“The Scientist and Engineer's Guide to Digital Signal Processing” turned into an EPUB ebook

The book “The Scientist and Engineer's Guide to Digital Signal Processing” by Steven W. Smith, Ph.D. was recommended to me. I'm in the process of reading it and enjoy doing so. I recommend it myself.

Unfortunately, that book is not open-source. But it is available via the website http://www.dspguide.com/ and a license is kindly provided that allows, free of charge:

You may download any or all of the book in electronic form, for your personal use.

In my case, my preferred "personal use" is reading on my e-book reader.

The accompanying Rakefile contains the program that I used to download the book in electronic form and convert it into the ebook-reader EPUB format.

What does my programm do?

It

• downloads the book in electronic form from the website, including any graphics that are referenced (and exist on that website, see below),

• removes stuff of no value for my ebook-reader intention, such as navigation, Javascript and CSS-styles,

• scales all graphics (which are a bit small, see below) via CSS, and

• as its final result, creates an EPUB file dspguide.epub.

Intended uses of this repository

Among other things, you can use this repository to

• do the same as I did towards your own personal use of the book,

• look into the Rakefile for fun, learning, or to use it a basis for similar endeavours of your own.

Installation

To run this program, you first need to complete three installation tasks.

• You need a working installation of a reasonably recent Ruby.

• Into that installation, you need to integrate the Nokogiri gem.

• You also need a reasonably recent version of Calibre.

For what are those needed?

• The program rake, that comes with the Ruby installation, and Ruby itself are used to download things and for overall flow control.

• Nokogiri is used to manipulate the HTML that goes into the ebook conversion process, and also to determine which graphics are included.

• Of Calibre, what is actually used is the command-line program ebook-convert.

This was developed under Linux. I see no reason why this shouldn't work on Mac or even Windows.

I could easily come up with a Dockerfile, if there is demand for it. If you had a Dockerfile, you'd only need to install the one software Docker, as opposed to the three things you need to install presently.

How do you run this?

After you have cloned this repository and your installation is complete, open a terminal, navigate to the directory that contains the clone of this repository, more specifically, the Rakefile, and type

rake

Assuming you have internet connectivity, this should

• run a considerable amount of time (some minutes),

• entertain you with some messages, e.g., about the 34 chapters being downloaded, and about (a few) images referenced from the HTML that do not exist on the remote server,

• when completed, leave a lot of files in the directory, among them the file dspguide.epub.

Details you may or may not care about

Versions used by me

I myself have been using Debian GNU Linux (Jessie) to develop this, ruby 2.3.3 with Nokogiri 1.7.0.1 (both installed via rvm) and Calibre 2.75.1 (obtained from Jessie-backports).

The images

The book's text links to many images. Formulas and graphs are typically such images. On my ebook-reader, the writings in those images tend to be displayed with small letters on the border of readability. In the conversion process, I introduce specific styling to enlarge those images to 95% of the screen width, which improved matters somewhat. Some images are best viewed with the reader oriented horizontally, others vertically.

A few images referenced by the text do not exist on the remote server. This is a bug of the remote web site. A warning is issued for each such image that's found missing during download. Those missing image references are removed before the EPUB is generated. (I checked that my browser has the same problem when directly viewing the web site.)

Individual steps

You can do things step-wise. To learn what steps are available, see the output of rake -T .

Download the PDFs that make up the book

You can also use the Rakefile to download all chapter PDFs. For this, you need neither Nokogiri nor Calibre installed, just Ruby is enough. (For PDF download without Nokogiri installed, simply remove the line require 'nokogiri' near the top of the Rakefile.) Run

rake grab_all_pdfs

Using a cache (doesn't help much)

I've been running this software behind a squid cache, but www.dspguide.com isn't cache-friendly. While the graphics are cach-able, all HTML files are downloaded all over again on each run of the program.

This is work in progress

I whipped this together in a single evening and stopped coding when I considered the result good enough for my reading pleasure. The time that went into coding is comparable to the time that went into authoring this README. Further improvements (to both) are possible.

One obvious improvement would be to separate the HTML download and the HTML process, into separate steps. With that, the processing could be changed and re-run without the (present) need to repeat the download.

My Rakefile is open source under the Apache license. See the top of the Rakefile for details. It works for me, but, as is customary in open source, I do not guarantee anything.