downloadIamge(imgsrc) {
    // 下载png
    // 
    // 下载图片地址和图片名
    let image = new Image()
    // 解决跨域 Canvas 污染问题
    image.setAttribute('crossOrigin', 'anonymous')
    image.onload = function () {
      let canvas = document.createElement('canvas')
      canvas.width = image.width
      canvas.height = image.height
      let context = canvas.getContext('2d')
      context.drawImage(image, 0, 0, image.width, image.height)
      let url = canvas.toDataURL('image/png') // 得到图片的base64编码数据
    }
    image.src = imgsrc
}

参考文章