<script>
    function trans_base64(url,) {
      const img = url; //imgurl 就是你的图片路径

      function getBase64Image(img) {
        const canvas = document.createElement('canvas');
        canvas.width = img.width;
        canvas.height = img.height;
        const ctx = canvas.getContext('2d');
        ctx.drawImage(img, 0, 0, img.width, img.height);
        const ext = img.src.substring(img.src.lastIndexOf('.') + 1).toLowerCase();
        const dataURL = canvas.toDataURL('image/' + ext);
        return dataURL;
      }

      const image = new Image();
      image.setAttribute('crossOrigin', 'anonymous');
      image.src = img;
      image.onload = function () {
        var base64 = getBase64Image(image);
        fn(base64);
      };
    }
    trans_base64('./12.jpg', function (re) {
      console.log(re)
    })
  </script>