probe-image-size/lib/parse_stream/gif.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_GIF87a = str2arr('GIF87a')
var SIG_GIF89a = str2arr('GIF89a')


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

  parser._bytes(10, function (data) {
    parser._skipBytes(Infinity)

    if (!sliceEq(data, 0, SIG_GIF87a) && !sliceEq(data, 0, SIG_GIF89a)) {
      parser.push(null)
      return
    }

    parser.push({
      width: data.readUInt16LE(6),
      height: data.readUInt16LE(8),
      type: 'gif',
      mime: 'image/gif',
      wUnits: 'px',
      hUnits: 'px'
    })

    parser.push(null)
  })

  return parser
}