use promise instead of callback

promiseTest.js

async function checkImage (file, pixels, onSuccess, onFailed) {
  const {width, height} = pixels
  return new Promise((resolve, reject) => {
    try {
      const img = await readImageFromFile(file)

      if (img.width !== WIDTH || img.height !== HEIGHT) {
        alert(`图标文件必须 ${pixels} 像素`)
      } else {
        resolve(img)
      }
    } catch (e) {
      reject(e)
    }
  })
}

usage: checkImage().then(onResolve, onReject)
// you can use it as a normal promise.

with this method, you have to use it as a normal function:

checkImage(file, pixels, result => normal , error => exception)

Firstly, async function returns a promise object. return will be received as params of resolve, throw will be received as params of reject. Thus, you can get the result with await because it is just a promise.
Secondly, of course, you can use it as a normal function. However, you can't get result by calling the function, you have to treat it as a promise. the only way to get some results is callback--an ugly method.

with proper way

async function checkImage (file, pixels) {
  const {width, height} = pixels

  try {
    const img = await readImageFromFile(file)

    if (img.width !== WIDTH || img.height !== HEIGHT) {
      alert(`图标文件必须 ${pixels} 像素`)
    } else {
      return img
    }
  } catch (e) {
    throw e
    alert('读取图片文件失败')
  }
}

you can use it following :

let result = await checkImage(file, pixels)

or

checkImage(file, pixels).then(result => normal, error => exception)