It would be great if I could "query" each individual point to see it's info - like the exact pixel position. Maybe a right-click? I'll keep working with it, but this is very cool!

Nice idea Jeff, I think this could work well as a little yellow popup tooltip that would appear when you roll over the points.

I've updated the application so that it now shows little tooltip popups when you move the mouse over each point or shape. The measurements are shown in the current units selected. If you download again you'll see the latest changes.

Also in this update is a background grid in the dropdown and bitmap export.

That's perfect. As I am trying it, of course, I thought...

I know it's more complicated, but it would be really useful if you could declare the absolute zero for both axes based on the image in use, rather than just the screen coordinates. I use this in my graphics programs - basically dragging the zero point of the rulers.

Just a thought.