Original SGB Border too big? about super-game-boy-border-converter

[marcrobledo]

Sadly, that's because of the quantization algorithm. Probably, the original border had a lot of tiles already, the quantization process can fail to get the exact data same as the original border.

You can try to disable dithering and use slow mode to get better results. Even you can keep trying with the same options, as the quantization process gives different results every time.

[marcrobledo]

I've tried with this image

By enabling High quality, some times you can get it under 256 tiles. Just keep clicking on Convert (this is because the quantization algorithm has some randomness). It can also be done without High quality, but it takes more tries.

The reason the converter fails most of the time in this case is because of the palette color order. This border has blank tiles for sea, clouds and sky. They are treated as different tiles. If due to the algorithm, at least two of their different colors happen to share the same color index (in different palettes), their data will be the same and will count as a unique tile, thus saving a single tile.
After observing the results, looks like this border ends up converted with 257 or 258 tiles most of the time, which means if the algorithm manages to save two tiles, then it will be under 256.

I can think of a few workarounds, none of them are trivial :-(