根据图片地址链接下载图片

/**
   * 根据图片链接下载图片
   */
  const downloadImg = () => {
    const canvas = document.createElement('canvas');
    const img = document.createElement('img');
    img.onload = () => {
      canvas.width = img.width;
      canvas.height = img.height;
      const context = canvas.getContext('2d');
      context.drawImage(img, 0, 0, img.width, img.height);
      canvas.getContext('2d').drawImage(img, 0, 0, img.width, img.height);
      canvas.toBlob(b => {
        const link = document.createElement('a');
        link.href = window.URL.createObjectURL(b);
        link.download = new Date().getTime().toString(); // 下载图片名称
        link.click();
      }, "image/jpeg");
    }
    img.setAttribute('crossOrigin', 'Anonymous');
    img.src = imgSrc;
  }