The combination of jspngopt and pako should eliminate possible causes for
different PNG encodings, although the core reason for #325 remains unknown.
Pako has poorer compression rates than native libz, but optimization can
counter that effect, and actually reduce the size of the screenshots.
The screenshots for LimitControls and UnsupportedCmds on Firefox used to
exhibit subpixel rendering before, for reasons unknown. The regenerated
versions don't exhibit this. See #324 for a discussion.
A fraction is surrounded by a box of width \nulldelimiterspace on either side.
That size is 1.2pt and does not scale with the style or font size.
Furthermore, a \frac creates a brace-enclosed group which results in a
\mathord, not a \mathinner.
Summary:
Using \phantom with non-phantom math in Perseus doesn't render to be the
same size because \phantom uses MathJax and the non-phantom math uses KaTeX.
Implementing \phantom in KaTeX should solve this alignment issue.
Test Plan:
[x] write (and run) unit tests
[x] create (and run) screenshotter tests
Reviewers: emily
Reviewed By: emily
Differential Revision: https://phabricator.khanacademy.org/D16720
