Nitro Character Studio
I’m still on the look out for this. This came with the official NDS SDK kit for DS/DSi. It’s a conversion tool that takes an image/bitmap as the input, and converts/outputs a tilemap, 8×8 tiles, and 16 subpalettes of 15 colors. Orion_ used this in one of his PC-Engine demos (slide show), a few years back.
I’ve gotten a hold of one leaked NDS SDK by Nintendo, but it was older and didn’t have the conversion app. If anyone has access to this or knows where to find it, let me know. No, I’m not interested in developing for DS platform. I just want the app, because the color reduction and sorting is superior to anything I’ve seen (including Quither and ProMotion).