L2-Norm in exrdiff

[mrecachinas]

Any plan to implement L2 norm in exrdiff? Or any known tools out there to do that? The RMS in exrdiff appears to be squaring the R, G, and B distances for each pixel, averaging them across the whole image, and taking the square root, whereas the average L2-norm squares the R, G, and B distances for each pixel, takes the square root of their sum, then averages that across the whole image.

I can whip up a working implementation that could be added if you're interested.