I left return there as a way to debug actually. I figured the problem has to do with multiplying based on two different size. I was expecting something like for x in first.image.width, for y in first.image.height, multiply first pixel by second image pixel.
After figuring it out, I upgraded Tiled Form/rep_form_pixel. It’s not exactly the best theoretical possible speed, but it is what I can do within g’mic limit. The best theoretical speed from what I recall seems to be .089 s, but that is if only mul command works with different size like I expected it to (it doesn’t, but not a bug either).
I think I realized how to do max, min on specified areas in context of rep_form_pixel. Right now, there’s only weighed average mode. If it turns out to be interesting, then I will update it, and I expect it to be the case that it is interesting. However, I’m wary of color space related issue with min, max, so it might have to be limited with rgb,rgb,cmyk in those cases.
This might take a while as I will factor into alpha channel and cmyka. Thanks to the help of @David_Tschumperle, I managed to implement max mode for rep_form_pixel.
See this thread for details: Return maximum value coordinates based from the sum of channel in a window in context of fill block. - #6 by David_Tschumperle
Left - Original ; Middle Left - Minimum ; Middle Right - Maximum ; Right - Average