Went a bit further down the rabbit hole and found the previous devlogs he posted about the topic for anyone interested. [1] [2] Of note was an upsampling algorithm called Scale2X he talked about. [3] Pretty neat !

[1] https://forums.tigsource.com/index.php?topic=40832.260 [2] https://forums.tigsource.com/index.php?topic=40832.msg121719... [3] https://www.scale2x.it