图片转换成base64

let bgcImage = 'http://192.168.0.83:9080/files/4a9c3056-9b9b-4b41-b8e2-fd9f27023c41.jpg'
let image = new Image()
    image.crossOrigin = '' // 必须有这个
    image.src = bgcImage
    image.onload = () => { // 图片加载完成后，调用getBase64Image方法
        let base64ImageSrc = getBase64Image(image)
        console.log(base64ImageSrc )
}

// url转base64
export function getBase64Image(image, width, height) { // width、height调用时传入具体像素值，控制大小 ,不传则默认图像大小
  let canvas = document.createElement('canvas')
  canvas.width = width !== undefined ? width : image.width
  canvas.height = height !== undefined ? height : image.height
  let ctx = canvas.getContext('2d')
  ctx.drawImage(image, , , canvas.width, canvas.height)
  let ext = image.src.substring(image.src.lastIndexOf('.') + ).toLowerCase()
  let dataURL = canvas.toDataURL('image/' + ext)
  return dataURL
}

// base64转file
export function dataURLtoFile (dataurl, filename) {
  let arr = dataurl.split(',')
  let mime = arr[].match(/:(.*?);/)[]
  let bstr = atob(arr[])
  let n = bstr.length
  let u8arr = new Uint8Array(n)
  while (n--) {
    u8arr[n] = bstr.charCodeAt(n)
  }
  return new File([u8arr], filename, { type: mime })
}