GIMP: find midpoint / arbitrary division between two points

Question

How do I find the middle, or n/th division or percentage of distance between two arbitrary points in GIMP?

Like, I have an object / a line of arbitrary length / two guides, placed in arbitrary place of the image. I want to place an object/marker/guide/whatever right in the middle of it, or precisely at 1/3 of it, and I want to do it with a bit of precision, not "by eye".

Is there any easier way than finding the pixel locations of the ends of the line and calculating proportions in a calculator on the side, or using Thales Theorem to "construct" the point?

(the one I found: draw a line the full distance on a separate layer, then use the "scale" tool to scale it by given percentage... but it feels extremely clunky)

Answer 1

Your method already seems like the best way to do it (using coordinates and calculator that is).

However, if you need to do it for too many items you could write a gimp-script that saves you time. Here's a tutorial on how to write those : http://gimp.open-source-solution.org/manual/gimp-using-script-fu-tutorial-first-script.html

Answer 2

duplicate backround layer and scale it by 50 percent width and height then drag this smaller layer into a corner ofthe background layer you get the middle point