probe-image-size/lib/parse_sync/avif.js

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

// Utils used to parse miaf-based files (avif/heic/heif)
//
//  - image collections are not supported (only last size is reported)
//  - images with metadata encoded after image data are not supported
//  - images without any `ispe` box are not supported
//


'use strict'


var str2arr = require('../common').str2arr
var sliceEq = require('../common').sliceEq
var readUInt32BE = require('../common').readUInt32BE
var miaf = require('../miaf_utils')
var exif = require('../exif_utils')

var SIG_FTYP = str2arr('ftyp')


module.exports = function (data) {
  // ISO media file (avif format) starts with ftyp box:
  // 0000 0020 6674 7970 6176 6966
  //  (length)  f t  y p  a v  i f
  //
  if (!sliceEq(data, 4, SIG_FTYP)) return

  var firstBox = miaf.unbox(data, 0)
  if (!firstBox) return

  var fileType = miaf.getMimeType(firstBox.data)
  if (!fileType) return

  var meta
  var offset = firstBox.end

  for (;;) {
    var box = miaf.unbox(data, offset)
    if (!box) break
    offset = box.end

    // mdat block SHOULD be last (but not strictly required),
    // so it's unlikely that metadata is after it
    if (box.boxtype === 'mdat') return
    if (box.boxtype === 'meta') {
      meta = box.data
      break
    }
  }

  if (!meta) return

  var imgSize = miaf.readSizeFromMeta(meta)

  if (!imgSize) return

  var result = {
    width: imgSize.width,
    height: imgSize.height,
    type: fileType.type,
    mime: fileType.mime,
    wUnits: 'px',
    hUnits: 'px'
  }

  if (imgSize.variants.length > 1) {
    result.variants = imgSize.variants
  }

  if (imgSize.orientation) {
    result.orientation = imgSize.orientation
  }

  if (imgSize.exif_location &&
      imgSize.exif_location.offset + imgSize.exif_location.length <= data.length) {
    var sig_offset = readUInt32BE(data, imgSize.exif_location.offset)
    var exif_data = data.slice(
      imgSize.exif_location.offset + sig_offset + 4,
      imgSize.exif_location.offset + imgSize.exif_location.length)

    var orientation = exif.get_orientation(exif_data)

    if (orientation > 0) result.orientation = orientation
  }

  return result
}