svg2ttf/lib/ttf/tables/head.js

Converts SVG font to TTF font

'use strict'

// See documentation here: http://www.microsoft.com/typography/otspec/head.htm

var ByteBuffer = require('microbuffer')

function dateToUInt64 (date) {
  var startDate = new Date('1904-01-01T00:00:00.000Z')

  return Math.floor((date - startDate) / 1000)
}

function createHeadTable (font) {
  var buf = new ByteBuffer(54) // fixed table length

  buf.writeInt32(0x10000) // version
  buf.writeInt32(font.revision * 0x10000) // fontRevision
  buf.writeUint32(0) // checkSumAdjustment
  buf.writeUint32(0x5F0F3CF5) // magicNumber
  // FLag meanings:
  // Bit 0: Baseline for font at y=0;
  // Bit 1: Left sidebearing point at x=0;
  // Bit 3: Force ppem to integer values for all internal scaler math; may use fractional ppem sizes if this bit is clear;
  buf.writeUint16(0x000B) // flags
  buf.writeUint16(font.unitsPerEm) // unitsPerEm
  buf.writeUint64(dateToUInt64(font.createdDate)) // created
  buf.writeUint64(dateToUInt64(font.modifiedDate)) // modified
  buf.writeInt16(font.xMin) // xMin
  buf.writeInt16(font.yMin) // yMin
  buf.writeInt16(font.xMax) // xMax
  buf.writeInt16(font.yMax) // yMax
  buf.writeUint16(font.macStyle) // macStyle
  buf.writeUint16(font.lowestRecPPEM) // lowestRecPPEM
  buf.writeInt16(2) // fontDirectionHint
  buf.writeInt16(font.ttf_glyph_size < 0x20000 ? 0 : 1) // indexToLocFormat, 0 for short offsets, 1 for long offsets
  buf.writeInt16(0) // glyphDataFormat

  return buf
}

module.exports = createHeadTable