Create an Image from URL - Social Sharing

Hello All,

I am trying to implement social sharing for my app. I am using amazon to get images with 20 seconds expiration time. The problem is, when I share the link, the link expires soon. I am trying to create an image on the fly when the image is first loaded. All I have is image url. How can I convert it to Base64? Is there any way of doing that? Because, whenever I try to get the same URL using HttpClient get method, unknown error returns from the remote-end. Your advices would be appreciated.

Thanks in advance.