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agyeiarcher / Crispy-VF

Crispy is a variable font
SIL Open Font License 1.1
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Calibrate Grade values in terms of Weight axis units #77

Open davelab6 opened 3 years ago

davelab6 commented 3 years ago

https://github.com/google/fonts/blob/main/axisregistry/grade.textproto is the definition of the axis for Google Fonts, which uses wght axis units - relative to default - for grade.

But currently this project uses the initial -1.0..1.0 range that @dberlow initially proposed. So, now that the range in font units (UPM unit) is established, please calibrate Grade values in terms of Weight axis units.

Also, @dberlow wrote a guide to drawing grade in https://github.com/googlefonts/gf-docs/tree/main/Grade. @m4rc1e please could you explain how to do this calibration, perhaps as a PR to that doc?

davelab6 commented 3 years ago

Correction, as we can see in https://www.axis-praxis.org/specimens/amstelvar the original grade range proposal by @dberlow was parametric -- per mille of em.

Parametric values for this particular axis made it possible For a single value to be given for, e.g. dark mode correction, regardless of the typeface, or style, and accurate to its weight width and opsz, among all other fonts with compatible values for grade, in the future.

That is not what google wanted, which is where the -1 0 1 came from. From there, the current equally Difficult-to-finesse value system was decided.