base64toFile(dataUrl, fileName) {
const arr = dataUrl.split(',')
const mime = arr[0].match(/:(.*?);/)[1]
const bstr = window.atob(arr[1]) // base64编码
let n = bstr.length
const u8arr = new Uint8Array(n)
while (n--) {
u8arr[n] = bstr.charCodeAt(n) // unicode 编码
}
return new File([u8arr], `${fileName}.png`, {
type: mime
})
},