首先加载低分辨率背景图像，然后加载高分辨率背景图像

I am trying to optimize the size of my site when it is being outputted to the client. I am down to 1.9MB and 29KB when caching. The issue is that the first load contains an image which is very unoptimized for mobile devices; it has a 1080p resolution.I am trying to optimize the size of my site whe