Inverting Grayscale measurement scale

[Chemtech]

I'm working on making digital negative exposure curves for alternate photo processes.  Tutorials showing new curve creation using a step wedge show the step wedge scanned as 8-bit grayscale and loaded into PS, then the steps are measured using the Info window with white measuring 0% and black 100%.  I'm obviously trying to use GIMP and the grayscale measure tool measures the white step as 100% and the black as 0%.  Is there a way to invert the GIMP measurement scale so the white is measured as 0% and the black as 100%?  Or is Color>Invert the step wedge, and measure that, the only solution?
Thanks.
GT

[rich2005]

Keep looking in and maybe an expert will answer.

I looked at this https://afterness.com/digital/step_scale.html  and just a posterized gradient.

However,  taking this statement  quote Is there a way to invert the GIMP measurement scale so the white is measured as 0% and the black as 100%?

   

Using Colors -> Levels I can use the Black Point picker (1) to select white and the White Point picker (2) to select black
Then sent that to the Curves tool (3)  
..............but how that applies to your step-scale I do not know.