FreeType Versus STBTT

bwip-js version 1.0 used the FreeType font engine, using emscripten to cross-compile to JavaScript. FreeType is an amazing piece of software, with built in auto-hinting and tons of special font rendering strategies.

bwip-js version 2.0 uses stb_truetype.h, compiled using the cheerp cross-compiler. STBTT is equally amazing software. It is a single, ~4500 line file (a large majority being comments), yet it produces excellent letter forms, even at small sizes.

Here is a comparison at scale=2, which corresponds to a 20px/15pt effective font size:

The STBTT letter forms are slightly heavier stroked than FreeType's and a bit fuzzier, but both are highly legible. Considering the complexity of font rendering, that is a pretty respectable result for STBTT. Now lets look at compiled code size:

$ ls -l freetype.js fontlib.js
-rw-rw-r-x  1 bwip-js users 1394208 Sep 19  2016 freetype.js
-rw-rw-r--  1 bwip-js users  103734 Oct 16 14:51 fontlib.js

The above js-files both contain the embedded OCR fonts (about 54K bytes), plus the respective font rendering libraries.

Run time memory usage is drastically different as well. Emscripten pre-allocates a 16MB block of memory (as an ArrayBuffer) that caused issues with using bwip-js on embedded servers, while cheerp uses a traditional allocate-as-you-go memory model that is considerably easier on resources.