probe-image-size/lib/parse_stream/tiff.js

Get image size without full download (JPG, GIF, PNG, WebP, BMP, TIFF, PSD)

'use strict'


var ParserStream = require('../common').ParserStream
var str2arr = require('../common').str2arr
var sliceEq = require('../common').sliceEq


var SIG_1 = str2arr('II\x2A\0')
var SIG_2 = str2arr('MM\0\x2A')


function readUInt16 (buffer, offset, is_big_endian) {
  return is_big_endian ? buffer.readUInt16BE(offset) : buffer.readUInt16LE(offset)
}

function readUInt32 (buffer, offset, is_big_endian) {
  return is_big_endian ? buffer.readUInt32BE(offset) : buffer.readUInt32LE(offset)
}

function readIFDValue (data, data_offset, is_big_endian) {
  var type = readUInt16(data, data_offset + 2, is_big_endian)
  var values = readUInt32(data, data_offset + 4, is_big_endian)

  if (values !== 1 || (type !== 3 && type !== 4)) {
    return null
  }

  if (type === 3) {
    return readUInt16(data, data_offset + 8, is_big_endian)
  }

  return readUInt32(data, data_offset + 8, is_big_endian)
}

module.exports = function () {
  var parser = new ParserStream()

  // read header
  parser._bytes(8, function (data) {
    // check TIFF signature
    if (!sliceEq(data, 0, SIG_1) && !sliceEq(data, 0, SIG_2)) {
      parser._skipBytes(Infinity)
      parser.push(null)
      return
    }

    var is_big_endian = (data[0] === 77 /* 'MM' */)
    var count = readUInt32(data, 4, is_big_endian) - 8

    if (count < 0) {
      parser._skipBytes(Infinity)
      parser.push(null)
      return
    }

    function safeSkip (parser, count, callback) {
      if (count === 0) { // parser._skipBytes throws error if count === 0
        callback()
        return
      }

      parser._skipBytes(count, callback)
    }

    // skip until IFD
    safeSkip(parser, count, function () {
      // read number of IFD entries
      parser._bytes(2, function (data) {
        var ifd_size = readUInt16(data, 0, is_big_endian) * 12

        if (ifd_size <= 0) {
          parser._skipBytes(Infinity)
          parser.push(null)
          return
        }

        // read all IFD entries
        parser._bytes(ifd_size, function (data) {
          parser._skipBytes(Infinity)

          var i, width, height, tag

          for (i = 0; i < ifd_size; i += 12) {
            tag = readUInt16(data, i, is_big_endian)

            if (tag === 256) {
              width = readIFDValue(data, i, is_big_endian)
            } else if (tag === 257) {
              height = readIFDValue(data, i, is_big_endian)
            }
          }

          if (width && height) {
            parser.push({
              width: width,
              height: height,
              type: 'tiff',
              mime: 'image/tiff',
              wUnits: 'px',
              hUnits: 'px'
            })
          }

          parser.push(null)
        })
      })
    })
  })

  return parser
}