Engine

[digitalethics]

How is this engine different from epub.js and readium-js for rendering epubs? Would you mind sharing more background information on your technical choices?

[baldurbjarnason]

It'd be my pleasure to share some details on why we went with this approach.

The first difference is that it's younger, less mature, and still in development 🙂

If we assume that I'll be able to get ink-engine to a point where I'm happy with it's design and maturity, it diverges from readium-js and epub.js in a number of ways because we have very different goals. Many of those goals are a bit specialised so odds are that most people would be better served by other solutions.

ink-engine's goals:

• Mostly server-side rendered (SSR). By doing most of the format processing on upload (in a cloud function/lambda) and in an on-demand pre-render function, you should be able to use ink-engine to build web app reading features that require very little javascript on the front end. Inevitably, this means that we will support fewer features than readium-js or epub.js but hopefully the web app will run relatively fast on more devices instead. The long term goal is that you should even be able to use it to create no-JS statically rendered web-books from common document formats. Most projects really don't need this tradeoff.
• Multi-format support. Because we only plan on supporting a smaller set of features it's easier for us to support more formats. We already support docx and I plan on supporting a lot more markup-based formats once the API and design is more settled. It's important to us to have reader support for document formats commonly used for writing because in academia and research the reading and writing processes are very tightly interwoven.
• No pagination. We believe that in-browser pagination has a number of hard-to-solve layout and performance issues and that until those issues are resolved (and maybe even after, we're fans of the scroll) research-oriented reading is better served by trying to build a really good scrolling reader instead.
• ink-engine is just a server-side processing engine, not a reader. It's not nearly as 'plug-and-play' as epub.js or readium-js. At some point I'd like to write up some documentation for how to build a SSRed web-based reader using ink-engine but we haven't reached that point yet 🙂.

To make a long story short: unless you need server-side rendering, document format support, prefer scrolling, and have the time and resources for a little bit more involved implementation, you probably won't find ink-engine particularly useful. Both epub.js and readium-js are excellent tools and they will both always have better support for a broader set of EPUB features than ink-engine.

If you do need all of those things then ink-engine will be exactly the library for you!

Once I've stopped tweaking the intermediary format it generates, that is. The cloud function/lambda upload processor generates an intermediate JSON format based on Web Publications and UnifiedJS's hast HTML-oriented abstract syntax tree JSON format. That format is common to all of the formats we support and the design for it is still very much in flux.