export-kerning/index.js

Exports the kerning of an OpenType font

#!/usr/bin/env node

import fs from 'fs';
import opentype from 'opentype.js';
import { Command } from 'commander';
import { exportKerning } from './core.js';

const program = new Command();

program
  .name('export-kerning')
  .description('Export kerning information from OpenType fonts')
  .argument('<font-file>', 'Path to the font file')
  .option('-o, --output <file>', 'Output file path', 'output/kerning.json')
  .option('-t, --text <text>', 'Text to analyze for kerning pairs', null)
  .option('-r, --ranges <ranges>', 'Unicode ranges to analyze', null)
  .action(async (fontPath, options) => {
    try {
      const font = await opentype.load(fontPath);

      // Use the exportKerning function
      const result = exportKerning(font, {
        ranges: options.ranges || null,
        text: options.text || null
      });

      // Save main kerning file
      const mainData = {
        unitsPerEm: result.unitsPerEm,
        kerningPairs: result.kerningPairs
      };
      fs.writeFileSync(options.output, JSON.stringify(mainData));
      console.log(`✔️ Optimized kerning pairs saved to ${options.output}`);

      // If subset was generated, save it
      if (result.subset) {
        const subsetOutput = options.output.replace(/\.[^.]+$/, '-subset$&');
        fs.writeFileSync(subsetOutput, JSON.stringify(result.subset));
        console.log(`✔️ Optimized used kerning subset saved to ${subsetOutput}`);
      }
    } catch (err) {
      console.error('Error:', err.message || err);
      if (err.stack) console.error(err.stack);
      process.exit(1);
    }
  });

program.parse();