Plugin for measurement tools on an image?

Before I start building something from scratch, I’m wondering if there is a plugin anywhere that has tools that function like Photoshop’s guides - basically ruler guides that can be dragged from the left and right, top and bottom edges of a frame, in order to mark/measure features in an image.

Just a heads up, The Iconfactory has a patent on this technology

hmm. Photoshop has had the kind of measurement tools I’m talking about since the early 1990s (maybe even earlier), and this patent is dated 2008. I think this is talking about something different, but the way it’s written isn’t exactly clear.

The feature I want exists in a lot of applications that have been around since before Photoshop, even, but the way I’m reading the patent, any display of the X,Y deltas from the starting X,Y position would constitute a “measurement.” I don’t think that’s right.

Essentially what I want to do is draw a line on a picture and know where it is, then another line in another location, then drag a box between them to get the number of pixels. Every graphics tool that allows you to draw a box tells you how big that is in pixels, as you’re doing it. To be clear, I’m not looking to do something like a phone-based measurement tool for real-life objects or anything like that. What I want is to measure the number of pixels between two lines drawn on an image.

I know I can easily do this, just looking for a shortcut so I don’t have to deal with it.