I am using Google Charts to display charting data in my application. Sometimes Google is slow and the charts will take a while to load. This scenario seems to be a common en
Preloading is not the way to go. If your image is directly visible in your application, your browser will load it as fast as possible and will not be able to load it faster using Javascript.
What you can do is to load it slower.
You seem to consider the image loading is slow because you want it to be immediate. Hard to be faster than immediate.
Maybe you can try the other way. Design your application so that the chart is displayed when the user interacts with something (click a button, a link, etc.), then load the chart whenever the user asks for it.
I see 2 advantages to this, mainly for low bandwidth users (mobile users?):
Idea shamelessly stolen from AppleInsider mobile-version