How to automate unity editor screen grabs

I'd like to improve my shader documentation and one thing that I think would be very useful is to have a tool that will automatically render a screen grab from the 'Game' view.

Ideally, the script would walk through each attribute on a shader, and take a screen shot for different values of each shader attribute.

Then, I'll compile all these screenshots into better shader docs.,I want to automate some shader documentation, so one thing that I think would be very useful is a way to step through different shader settings and then take a screen grab, from the 'Game' view, for each setting of a shader attribute.

How would I go about writing this script for the Unity Editor?