Generate otfcc font dump out of a folder of images

base.json

{
    "head": {
        "version": 1.0,
        "fontRevision": 1.0,
        "flags": {
            "baselineAtY_0": true,
            "alwaysUseIntegerSize": true
        },
        "unitsPerEm": 1000,
        "macStyle": {},
        "lowestRecPPEM": 8,
        "indexToLocFormat": 0,
        "glyphDataFormat": 0
    },
    "hhea": {
        "version": 1.0,
        "ascender": 850,
        "descender": -150,
        "lineGap": 0,
        "caretSlopeRise": 1,
        "caretSlopeRun": 0,
        "caretOffset": 0
    },
    "vhea": {
        "version": 1.0,
        "ascent": 500,
        "descent": -500,
        "lineGap": 0,
        "caretSlopeRise": 0,
        "caretSlopeRun": 1,
        "caretOffset": 0
    },
    "post": {
        "version": 3.0,
        "italicAngle": 0,
        "underlinePosition": -100,
        "underlineThickness": 50,
        "isFixedPitch": false
    },
    "OS_2": {
        "version": 3,
        "usWeightClass": 400,
        "usWidthClass": 5,
        "fsType": {},
        "ySubscriptXSize": 650,
        "ySubscriptYSize": 600,
        "ySubscriptXOffset": 0,
        "ySubscriptYOffset": 75,
        "ySupscriptXSize": 650,
        "ySupscriptYSize": 600,
        "ySupscriptXOffset": 0,
        "ySupscriptYOffset": 350,
        "yStrikeoutSize": 45,
        "yStrikeoutPosition": 250,
        "sFamilyClass": 0,
        "panose": [
            2,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0
        ],
        "ulUnicodeRange2": {
            "CJK_Compatibility": true,
            "CJK_Unified_Ideographs": true
        },
        "achVendID": "TEST",
        "fsSelection": {
            "regular": true
        },
        "usFirstCharIndex": 32,
        "usLastCharIndex": 65509,
        "sTypoAscender": 850,
        "sTypoDescender": -150,
        "sTypoLineGap": 1000,
        "usWinAscent": 861,
        "usWinDescent": 220,
        "ulCodePageRange1": {
            "latin1": true,
            "latin2": true,
            "gbk": true
        },
        "ulCodePageRange2": {},
        "sxHeight": 480,
        "sCapHeight": 700,
        "usDefaultChar": 0,
        "usBreakChar": 32,
        "usMaxContext": 1,
        "usLowerOpticalPointSize": 0,
        "usUpperOpticalPointSize": 0
    },
    "name": [
        {
            "platformID": 1,
            "encodingID": 0,
            "languageID": 0,
            "nameID": 0,
            "nameString": "${COPYRIGHT}"
        },
        {
            "platformID": 1,
            "encodingID": 0,
            "languageID": 0,
            "nameID": 1,
            "nameString": "${FONTNAME}"
        },
        {
            "platformID": 1,
            "encodingID": 0,
            "languageID": 0,
            "nameID": 2,
            "nameString": "Regular"
        },
        {
            "platformID": 1,
            "encodingID": 0,
            "languageID": 0,
            "nameID": 3,
            "nameString": "${FONTIDENTIFIER}"
        },
        {
            "platformID": 1,
            "encodingID": 0,
            "languageID": 0,
            "nameID": 4,
            "nameString": "${FONTNAME}"
        },
        {
            "platformID": 1,
            "encodingID": 0,
            "languageID": 0,
            "nameID": 5,
            "nameString": "Version 1.00"
        },
        {
            "platformID": 1,
            "encodingID": 0,
            "languageID": 0,
            "nameID": 6,
            "nameString": "${FONTIDENTIFIER}"
        },
        {
            "platformID": 3,
            "encodingID": 1,
            "languageID": 1033,
            "nameID": 0,
            "nameString": "${COPYRIGHT}"
        },
        {
            "platformID": 3,
            "encodingID": 1,
            "languageID": 1033,
            "nameID": 1,
            "nameString": "${FONTNAME}"
        },
        {
            "platformID": 3,
            "encodingID": 1,
            "languageID": 1033,
            "nameID": 2,
            "nameString": "Regular"
        },
        {
            "platformID": 3,
            "encodingID": 1,
            "languageID": 1033,
            "nameID": 3,
            "nameString": "${FONTIDENTIFIER}"
        },
        {
            "platformID": 3,
            "encodingID": 1,
            "languageID": 1033,
            "nameID": 4,
            "nameString": "${FONTNAME}"
        },
        {
            "platformID": 3,
            "encodingID": 1,
            "languageID": 1033,
            "nameID": 5,
            "nameString": "Version 1.00"
        },
        {
            "platformID": 3,
            "encodingID": 1,
            "languageID": 1033,
            "nameID": 6,
            "nameString": "${FONTIDENTIFIER}"
        },
        {
            "platformID": 3,
            "encodingID": 1,
            "languageID": 2052,
            "nameID": 0,
            "nameString": "${COPYRIGHT}"
        },
        {
            "platformID": 3,
            "encodingID": 1,
            "languageID": 2052,
            "nameID": 1,
            "nameString": "${FONTNAME_ZH}"
        },
        {
            "platformID": 3,
            "encodingID": 1,
            "languageID": 2052,
            "nameID": 2,
            "nameString": "Regular"
        },
        {
            "platformID": 3,
            "encodingID": 1,
            "languageID": 2052,
            "nameID": 4,
            "nameString": "${FONTNAME_ZH}"
        }
    ],
    "cmap": {
        "U+0020": "space"
    },
    "CFF_": {
        "isCID": true,
        "${FONTNAME}": "${FONTIDENTIFIER}",
        "fullName": "${FONTIDENTIFIER}",
        "cidRegistry": "Adobe",
        "cidOrdering": "Identity",
        "cidSupplement": 0,
        "fdArray": {
            "${FONTIDENTIFIER}": {
                "privates": {
                    "defaultWidthX": 1000.0,
                    "nominalWidthX": 853
                }
            }
        }
    },
    "glyf": {
        ".notdef": {
            "advanceWidth": 1000,
            "advanceHeight": 1000,
            "verticalOrigin": 850,
            "CFF_fdSelect": "${FONTIDENTIFIER}",
            "CFF_CID": 0
        },
        "space": {
            "advanceWidth": 300
        }
    }
}

trace.py

import json
import potrace
import numpy as np
from skimage import io, transform

def trace(filename, baseline=150, upm=1000):
  img = io.imread(filename)
  if len(img.shape) > 2: img = img[:,:,0]
  h, w = img.shape
  resized = transform.resize(img, (int(upm), int(upm/h*w))) < 0.5
  bmp = potrace.Bitmap(resized)
  path = bmp.trace()
  contours = []
  for curve in path:
    contour = []
    for segment in curve:
      if not segment.is_corner:
        contour.insert(0, {
          'x': int(segment.c1[0] + 0.5),
          'y': int(upm - segment.c1[1] - int(baseline) + 0.5),
          'on': False
        })
        contour.insert(0, {
          'x': int(segment.c2[0] + 0.5),
          'y': int(upm - segment.c2[1] - int(baseline) + 0.5),
          'on': False
        })
      contour.insert(0, {
        'x': int(segment.end_point[0] + 0.5),
        'y': int(upm - segment.end_point[1] - int(baseline) + 0.5),
        'on': True
      })
    contours.append(contour)
  return contours

def build_font(glyph_dict, copyright='Copyright 2021 Next Lab',
fontname='Test font', fontname_zh='测试字体', font_identifier='TESTFONT'):
  font_base = open('base.json').read()
  font_base = font_base.replace('${COPYRIGHT}', copyright)
  font_base = font_base.replace('${FONTNAME}', fontname)
  font_base = font_base.replace('${FONTNAME_ZH}', fontname_zh)
  font_base = font_base.replace('${FONTIDENTIFIER}', font_identifier)
  font_obj = json.loads(font_base)
  for unicode in glyph_dict:
    upper = unicode.upper()
    contours = glyph_dict[unicode]
    font_obj['cmap']['U+'+ upper] = 'uni' + upper
    font_obj['glyf']['uni' + upper] = {
      'advanceWidth': 1000,
      'advanceHeight': 1000,
      'verticalOrigin': 850,
      'CFF_fdSelect': font_identifier,
      'CFF_CID': 0,
      'contours': contours
    }
  return font_obj

import os
import multiprocessing as mp
files = os.listdir('yan')

if __name__ == '__main__':
  manager = mp.Manager()
  glyph_dict = manager.dict()

  def process(filename):
    char = filename.split('_')[1][0]
    unicode = '%X' % ord(char)
    glyph_dict[unicode] = trace('yan/' + filename)

  with mp.Pool(processes=8) as p:
    p.map(process, files)

  out_file = open('export.json', 'w')
  json.dump(
    build_font(glyph_dict.copy(), fontname='Next Lab Yan', font_identifier='NextLabYan', fontname_zh='Next Lab 颜体'),
    out_file
  )