Yammer预览图像

Question

我正在使用此处提供的代码https://developer.yammer.com/docs/share-button#分享存储在我的SharePoint页面上的文章给Yammer。问题是Yammer上的缩略图预览没有出现，我相信这是因为您需要登录才能查看文章，即当我将网址设置为google.com时，Google图像预览会显示，因为您无需登录。

有没有办法通过url发送图像或将图像位置（不受登录保护）或JSON对象发送到Yammer共享功能？ 即。

<script type="text/javascript">
  var options = {
    customButton : true, //false by default. Pass true if you are providing your own button to trigger the share popup
    classSelector: 'mybutton-css-class',//if customButton is true, you must pass the css class name of your button (so we can bind the click event for you)
    defaultMessage: 'My custom Message', //optionally pass a message to prepopulate your post
    pageUrl: 'www.microsoft.com', //current browser url is used by default. You can pass your own url if you want to generate the OG object from a different URL.
    previewImage: 'http://google.com/images/bestimageever.jpg'
  }; 
  yam.platform.yammerShare(options);
</script>

非常感谢！