If you wanna upscale images like Animal Crossing does this implements the algorithm it's most likely using: https://sourceforge.net/projects/xbrz/files/ScalerTest_1.1.zip
(Mac/ Windows/ Linux binaries)
There's also reference implementations for a number of emulators in the same Sourceforge, so that's cool
(via https://twitter.com/lunasorcery/status/1242569546038460416)