why would you scale them in the first are you using the software as some kind of magnifying glass before saving? it gets never boring with you dooes it 
Windows 10 scaling, man. For readability, smaller screens (less than 17" for 1080p?) will automatically scale everything up by some amount. In my case (1080p, 15.6"), it defaults to 125% scaling. I prefer it like this; 100% scaling is barely readable for me
with my glasses on.
The odd thing is that if you use Print Screen to screenshot (which I just prefer over Snipping Tool because I can go in and do pixel-perfect cropping), it scales it up from 1536 × 864 (1080p divided by 1.25) to 1920 × 1080, with all the blur that results from such a scaling. Things that look real sharp on my end look a bit blurry once I get the screenshot. This is why I put the width parameter in the [img] tag in screenshots to prevent scaling from screwing things up.
What I was testing is if there's any resampling method that would take this blurred 125% scaled image, then produces a perfect reproduction of the original at 100% scaling. There is none, as I said. I was using a checkerboard (1 pixel tall, 2 pixel wide) because that was an easy thing to work with.
Here's the one I was using, for reference. I copied the original, and I did a screenshot. That optical illusion came to me when I downscaled the screenshot down to its original size using Lanczos resampling, and zoomed in on it with Paint.net. I realized that the grid lines didn't look quite straight despite them being very straight.