I'm looking for a way to capture and visualize used disk space over time. All I need is one number– bytes used on disk. I store a lot of photos on my computer, so I need a way to estimate when I'll need more hard drive space. If there's a way to capture used disk space with hourly resolution that would be great, but even daily resolution is fine. I don't even need a visualization of the data; as long as the data is easily exportable to Excel, I can create my own graph and extrapolate.
I've seen many disk space visualization programs like WinDirStat and TreeSizeFree, but they don't have a way to automate capturing disk space usage over time.