图片url转base64

function getImgBase64(src){
    var base64="";
    var img = new Image();
    img.src= src;
    img.onload=function(){
        base64 = image2Base64(img);
        alert(base64);
    }
}
function image2Base64(img) {
    var canvas = document.createElement("canvas");
    canvas.width = img.width;
    canvas.height = img.height;
    var ctx = canvas.getContext("2d");
    ctx.drawImage(img, 0, 0, img.width, img.height);
    var dataURL = canvas.toDataURL("image/png");
    return dataURL;
}

base转file

export function Base64ToFile (dataurl: string, filename='截图') {
  let arr: any = dataurl.split(',');
  let mime = arr[0].match(/:(.*?);/)[1];
  let suffix = mime.split('/')[1];
  let bstr = atob(arr[1]);
  let n = bstr.length;
  let u8arr = new Uint8Array(n);
  while (n--) {
      u8arr[n] = bstr.charCodeAt(n);
  }
  return new File([u8arr], `${filename}.${suffix}`, {
      type: mime
  });
};