'use strict'

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

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

var readUInt32BE = require('../common').readUInt32BE

var SIG_PNG = str2arr('\x89PNG\r\n\x1a\n')

var SIG_IHDR = str2arr('IHDR')

module.exports = function (data) {

if (data.length < 24) return

// check PNG signature

if (!sliceEq(data, 0, SIG_PNG)) return

// check that first chunk is IHDR

if (!sliceEq(data, 12, SIG_IHDR)) return

return {

width: readUInt32BE(data, 16),

height: readUInt32BE(data, 20),

type: 'png',

mime: 'image/png',

wUnits: 'px',

hUnits: 'px'

}

}