Auto generated font from Randall's handwriting

[pelson]

As mentioned in #16, I have been playing with the handwriting sample provided by Randall, to see if we can auto-generate a decent font.

This PR pulls all of my work together. It:

• generates a new font-family, "xkcd Script", so that both the existing "xkcd" and "xkcd Script" may both be installed at the same time
• builds reproducibly on Travis using a docker container I prepared locally, containing:
  • pango
  • fontforge
  • python 2 (issues with python 3 and fontforge :cry:)
  • scikit-image
• pushes any changes to the font back into the repo (using doctr) so that we can have the built products alongside the code (e.g. the font itself, samples etc.)
  • a deploy key for ipython/xkcd-font will need to be created, and put in ``.github/deploy_key.enc in the format required by doctr

Recommended way of reviewing: Take a look around the branch at https://github.com/pelson/xkcd-font/tree/xkcd-script-v3

Here is the "handwriting sample" re-generated using the xkcd-script font:

There were a number of issues along the way:

• I'm currently unable to re-build the Dockerfile without getting Seg Faults (I guess something has moved under my feet, perhaps in conda-forge wrt. X11 but not confirmed. I sank several hours trying to fix, and in the end stuck with the image that I produced locally/originally). As a result, the Docker file is a bit embarrassing 😉 .
• I'm getting unexpected exit codes:
  • When generating the sfd file (but not when generating the exact same ttf file) I got 139 (SegFault from docker)
  • When generating the samples. I got 141 when generating the handwriting sample with non-ascii characters.

Known places where the work can be improved:

• There are glyphs in "xkcd" which could be copied into "xkcd Script"
• The code quality is very low - I have intentionally not refined it, and it shouldn't be hard to do
• The pipe character is currently the same as an "I" - I needed to do this to be able to put together the <| and |> ligatures. A font MUST have a glyph for each of the characters it has ligatures for.
• The glyph linewidth is too thick - some refinement of the potrace process (ppm -> svg) will be needed
• The glyphs spacing is too wide (necessary because the linewidth is currently so big). The ligatures therefore look a little too close, which of course they aren't because they are exactly spaced as per Randall's xkcd handwriting.
• Ligature spacing is too wide

Proposal: All of the above are known issues, I do not recommend improving the font in this PR, instead I'm keen to lay the foundations (i.e. merge), and iteratively improve (i.e. with small PRs)

Future decisions (I propose we resolve this after this PR):

• Do we need 2 fonts - should it just be "xkcd" and that's that? What about the fact that "xkcd" is significantly more uniform (perhaps unrealistically so)?
• Do we keep the build products inside the repo?
• Do we pull pelson/fontbuilder into the ipython namespace on Docker hub?

[pelson]

Incidentally, I tested I could have "xkcd", "xkcd Script" and "Humor Sans" all installed and used within matplotlib with:

import matplotlib.pyplot as plt
import matplotlib.font_manager

xkcd_regular = matplotlib.font_manager.FontProperties(family='xkcd', size=40)
xkcd_script = matplotlib.font_manager.FontProperties(family='xkcd Script', size=40)
humour_sans = matplotlib.font_manager.FontProperties(family='Humor Sans', size=40)

fig = plt.figure(figsize=(12.5, 3), dpi=100)
text = 'Hello XKCD world. BETTER?'
plt.figtext(0.01, 0.7, text + ' (xkcd)', transform=fig.transFigure, fontproperties=xkcd_regular)
plt.figtext(0.01, 0.4, text + ' (xkcd Script)', transform=fig.transFigure, fontproperties=xkcd_script)
plt.figtext(0.01, 0.1, text + ' (Humor Sans)', transform=fig.transFigure, fontproperties=humour_sans)
plt.show()

And got:

Note: Matplotlib cannot currently do ligatures, as can be seen in the word "BETTER".

[pelson]

Things I'd like to do next, preferably in another PR 😉 :

• [ ] Get doctr working on ipython/xkcd-font
• [x] Re-rename "xkcd-uniform" back to "xkcd" (docs and folder structure only, xkcd-uniform isn't in the font itself)
• [ ] Tweak and refine the READMEs a lot more, including generating a preview of "xkcd"
• [ ] Put together a CONTRIBUTING.md guide

[rgbkrk]

Proposal: All of the above are known issues, I do not recommend improving the font in this PR, instead I'm keen to lay the foundations (i.e. merge), and iteratively improve (i.e. with small PRs)

I'm sold on that.

[takluyver]

:+1: for merging and doing further improvements in another PR.

[pelson]

🎉 - thanks for moving it forwards guys.