Just use Magpie for games with lower resolution than your screen, Magpie upscaling is a lot better than default engine upscaling, i use it for everything, even old 640x480 VNs and RpgMaker games look almost like HD.
Interesting software. Thanks for the introduction. I play a lot of erotic rpg myself too, so this is a wonderful find.
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The original developer is Chinese it seems.
There is an English fork, but the fork is not up-to-date.
However, the program is in English anyway, so it doesn't matter.
I did a little test on Rance 3, since it is an old rpg game.
1 is windowed
2 is using Magpie upscale
3 is using the game own full screen option
We can observe that the way it is stretched is different.
The native option has some black border on the bottom in full screen. This shows that the program respects the aspect ratio when doing full screen and just padded the extra space with black.
While Magpie doesn't have those border, which is also true in the windowed option. This most likely means that Magpie calculated how to scale based on the windowed version.
The caveat is that since rance 3 is an old game, it is naturally a bit pixelated. so the difference in the quality is not properly shown.