Switch TeX renderer to CodeCogs

[adam-p]

The Google Image Charts API has been deprecated and could disappear at any time. This will wreck the rending of MDH math images. See discussion of alternatives in issue #144.

In the short term (and probably long term) we are going to switch to using CodeCodgs.

[cben]

[picking up from #144]

In exchange for that effort, I'll offer you this data point and possible solution to our woes: If you render to GIF instead of PNG (so, gif.latex), and you use \inline, the letters look... perfect.

I'm now skilled at finding a problematic example by typing into editor with any setting :-)
[though I'm yet to find any with default dpi]

vs

Will be back after I post the bug and some ideas about baselines on CodeCogs forums.

[cben]

BTW, I thougt Charts API will be gone around now but their deprecation notice has changed to:

Important: While the dynamic and interactive Google Charts are actively maintained, we officially deprecated the static Google Image Charts way back in 2012. This gives us the right to turn it off without notice, although we have no plans to do so.

[cben]

Reported at http://www.codecogs.com/pages/forums/pagegen.php?id=2870

A new gem is simultaneous under- and over- sized gifs:
http://latex.codecogs.com/gif.latex?%5Cdpi%7B200%7D%20z
http://latex.codecogs.com/gif.latex?%5Cdpi%7B200%7D%20a (this is the normal size)
http://latex.codecogs.com/gif.latex?%5Cdpi%7B200%7D%20N
:-)

[cben]

CodeCogs responded to that report in May 2015.
Back then I saw it became much better but I still caught a couple cases.
I now tried again and couldn't find any problems. Have you tried / seen any problems since then?

OTOH, google's deprecation notice has changed to this:

While the dynamic and interactive Google Charts are actively maintained, we officially deprecated the static Google Image Charts way back in 2012. This gives us the right to turn it off without notice, although we have no plans to do so.

so there is little pressure.

[cben]

FWIW there is a new notice saying:

Warning: This API is deprecated in 2012 and was turned off on March 18, 2019. Please use the actively maintained Google Charts API instead.

However the linked thread later says on March 20:

The API was turned back on temporarily and may be shut off again without notice.

😆 and https://chart.googleapis.com/chart?cht=tx&chl=\displaystyle\sum_{n=1}^\infty%20\frac{1}{n} works for me as of 2019-03-16.

Possibly they realized people need more warning, but they're absolutely not committing to any specific time it'll stay up, and clearly do intend to sunset it eventually...

• The 3rd-party https://www.image-charts.com advertized as "drop-in replacement" doesn't support LaTeX.

[cben]

Other options:

• https://upmath.me/ is powered by https://tex.s2cms.com which does very impressive stuff like supporting TikZ pictures, and tuned for high-quality svg, including a provision for communacating baseline height.
  Of course for email svg is still hopeless, so MDH would default to png, and current baseline

  from the FAQ there:

  Is it for free?

  Yep. In case of reasonable load, of course. If you obstruct other users, your requests will be blocked.

  How do I know if the service doesn’t stop working one day?

  You don’t. But I use it in my own projects and I’m not going to close it.

@parpalak, thanks for the high-quality project!
Do you think it'd be reasonable to default Markdown Here browser extension to use tex.s2cms.com?
Or do you recommend CodeCogs?

The extension's main use is probably for composing emails, but it's also usable on multiple blog / CMS sites.
It's important for the math to be readable years after the documents were created / sent — if you fear you'll to turn it off / block, it's better for MDH to choose CodeCogs now.
It's hard to estimate the extra load you'd get from this but basically, it'll keep increasing with time, and will be spread across many web sites.
@adam-p can you give any order of magnitude on MDH usage (and specifically math usage)?

P.S. the math image URLs generated by Markdown Here are configurable, and individuals will be able to point it to tex.s2cms.com anyway. The question is about defaults.