Oldstyle Figure Alignment Checker

Audit supplied numeral outlines for descenders and departures from lower observed median top; observed mixed alignment is not proof a font feature is oldstyle or correctly selected.

Description

Oldstyle-figure evidence can include descenders and varied tops.

Oldstyle-figure evidence can include descenders and varied tops. Observed geometry alone cannot verify an activated font feature.^[1]

Enter nonempty ordered min/max Y pairs and nonnegative baseline/top tolerances. Return indices below negative baseline tolerance or above reference+tolerance, lower median and any-deviation flag.

When to use Oldstyle Figure Alignment Checker

Use Oldstyle Figure Alignment Checker when you need to evaluate the supplied records under the calculation and evidence rules below. The even-sample reference is the lower middle value. No font feature, numeral identity or stylistic authenticity is established.

Prepare measured font or typeset-layout values and the explicit design policy requested. For text or font bytes, use the supported syntax explained below.

How to use Oldstyle Figure Alignment Checker and understand its results

Prepare measured font or typeset-layout values and the explicit design policy requested. For text or font bytes, use the supported syntax explained below.
Enter numeralGlyphYBounds, callerBaselineTolerance, callerTopTolerance using the field table and calculation rules, then run the tool.
Read descendingNumeralIndices, aboveLowerMedianNumeralTopIndices, lowerMedianObservedNumeralTop, mixedVerticalAlignmentObserved. The explanation below defines the units, signs, ordering and any flags or placeholder values.
If the tool reports an input issue, correct the values and run it again. Apply the stated assumptions when interpreting a successfully returned result.

Input field	Meaning	Value type; see rules below	Requirement
numeralGlyphYBounds	Numeral glyph y bounds	list of list of number	Required
callerBaselineTolerance	Caller baseline tolerance	number	Required
callerTopTolerance	Caller top tolerance	number	Required

Enter nonempty ordered min/max Y pairs and nonnegative baseline/top tolerances. Return indices below negative baseline tolerance or above reference+tolerance, lower median and any-deviation flag.

reference=lower median of sorted tops

Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.

Output field	Meaning	Value type
descendingNumeralIndices	Descending numeral indices	list of number
aboveLowerMedianNumeralTopIndices	Above lower median numeral top indices	list of number
lowerMedianObservedNumeralTop	Lower median observed numeral top	number
mixedVerticalAlignmentObserved	Mixed vertical alignment observed	boolean

json

{
  "input": {
    "numeralGlyphYBounds": [
      [
        -2,
        7
      ],
      [
        0,
        10
      ],
      [
        -2,
        7
      ],
      [
        0,
        7
      ]
    ],
    "callerBaselineTolerance": 0,
    "callerTopTolerance": 0
  },
  "output": {
    "descendingNumeralIndices": [
      0,
      2
    ],
    "aboveLowerMedianNumeralTopIndices": [
      1
    ],
    "lowerMedianObservedNumeralTop": 7,
    "mixedVerticalAlignmentObserved": true
  }
}

Limitations and assumptions

The even-sample reference is the lower middle value. No font feature, numeral identity or stylistic authenticity is established.

Numeric inputs, where present, must be finite. Follow the calculation-specific rules for overflow, underflow and exceptional cases. Matrices are limited to 128 rows and 128 entries per row. Numeric lists are limited to 10,000 entries; string lists to 128 strings of at most 128 characters each. The rules above may impose smaller limits. Missing required fields, extra fields, wrong value types and violations of the calculation rules are input errors. A successfully returned false flag is an evaluated outcome; its meaning is explained above.

Alternative or Complementary methods

Use Proportional vs Tabular Numeral Width Check: Tabular figures use equal advances, while proportional figures may differ. A calibration sample should remain distinct from full-digit coverage. For a complementary task, use Ascender/Descender Extents Checker: Glyph ink may extend beyond declared ascent and descent. Signed outline coordinates and positive descent magnitude have different roles.

References

Oldstyle Figure Alignment Checker — tool.io

Similar or alternative tools

Proportional vs Tabular Numeral Width Check
Tabular figures use equal advances, while proportional figures may differ. A calibration sample should remain distinct from full-digit coverage.
Ascender/Descender Extents Checker
Glyph ink may extend beyond declared ascent and descent. Signed outline coordinates and positive descent magnitude have different roles.