Measurements format
A data format to store definitions of font-level and glyph-level measurements.
Data structure
A measurement establishes a link between two points and allows us to calculate the distance between them.
The order of the points determine if the measurement is positive or negative.
Font-level measurements
- A font may contain multiple font-level measurements.
- Font measurement names must be unique.
- The order of the font measurements matters.
| attribute | description |
|---|---|
| name | name of the measurement |
| glyph 1 | name of the glyph containing the 1st measurement point |
| point 1 | index or shortcut of 1st measurement point |
| glyph 2 | name of the glyph containing the 2nd measurement point |
| point 2 | index or shortcut of 2nd measurement point |
| direction | direction of measurement |
| parent | parent measurement (optional) |
| description | description of this measurement (optional) |
Glyph-level measurements
- A glyph may contain multiple glyph-level measurements.
- Glyph measurement names are usually related to font-level measurements.
- Glyph measurement names must not be unique.
- Glyph measurement identifiers are created from the point indexes.
- The order of glyph measurements follows the order of font measurements.
| attribute | description |
|---|---|
| name | name of the measurement |
| point 1 | index or shortcut of 1st measurement point |
| point 2 | index or shortcut of 2nd measurement point |
| direction | direction of measurement |
Direction keys
The direction of measurement must be one of the following characters:
| characters | description |
|---|---|
| x | horizontal measurement |
| y | vertical measurement |
| a | angled measurement |
Point indexes or shortcuts
Point indexes are expressed as integers.
Font-level vertical metrics values are also acessible using the following shortcut characters:
| character | description | x | y |
|---|---|---|---|
| A | ascender | 0 |
font.info.ascender |
| B | baseline | 0 |
0 |
| C | cap height | 0 |
font.info.capHeight |
| D | descender | 0 |
font.info.descender |
| X | x-height | 0 |
font.info.xHeight |
Sign of the measured values
The sign of the measured values matters. While most measurements are usually positive, some are by definition negative – for example the descender value or a bottom overshoot.
If a font-level value is positive, and the measured glyph value is negative, we can suspect an issue with the contours (shapes turning inside out).
Python example
The key for font-level measurements is the name of the measurement.
fontMeasurements = {
'XTUC' : {
'glyph 1' : 'H',
'point 1' : 11,
'glyph 2' : 'H',
'point 2' : 8,
'direction' : 'x',
'parent' : 'XTRA',
},
# more font-level measurements here ...
}
The key for glyph-level measurements is an identifier created from the two point indexes.
glyphMeasurements = {
"a" : {
f'{ptIndex1} {ptIndex2}' : {
'name' : 'XTRA',
'direction' : 'x',
},
# more glyph-level measurements here ...
},
# more glyphs here ...
}
JSON format
Measurements can be stored in standalone JSON files using the format below.
The same set of measurement definitions can be used to measure all sources in a designspace.
{
"font": {
"XTUC": {
"direction": "x",
"glyph 1": "H",
"point 1": "11",
"glyph 2": "H",
"point 2": "8",
"parent": "XTRA"
},
/* more font-level measurements here ... */
},
"glyphs": {
"n": {
"0 20": {
"direction": "x",
"name": "XOLC"
},
"11 12": {
"direction": "x",
"name": "XOLC"
},
"13 19": {
"direction": "x",
"name": "XTLC"
},
/* more glyph-level measurements here ... */
},
/* more glyphs here ... */
},
}