Gameboy Development Forum

Tomi wrote:

hello guys,

what is the best way to copy a picture's tile data and map data when background display is from $8800 ? (signed)

1. generate signed map data with the graphics tools (I did not find this option in any of the tools)  and copy tile data starting at $8800

2. generate unsigned map data with graphic tool and then convert  somehow map data to signed in a second step  and copy tile data starting at $8800

3. generate unsigned map data with graphic tool and copy tile (16x128=2048) data starting at $9000 and the rest starting at $8800

4. ?

A large part of the problem is the tile data you want to convert. In my experience, RGBGFX is better for images that only contain a single palette (= DMG and single-palette CGB), whereas SuperFamiconv is better at multi-palette images.

SuperFamiconv handles "signed" map data just fine, you "simply" need to specify an offset of 0x80 when generating the tilemap. (It's a bit complex to use, but I can point at Makefile fragments for this)

RGBGFX only handles unsigned tile data, but you can get around this using "partial" INCBIN (though I'll agree it's not ideal), or a "bit 7 flip" script. The former is as simple as

INCBIN "file.2bpp", 16 * 128, 16 * <remaining amount of tiles> ; Include the "second half" of tiles
INCBIN "file.2bpp", 0, 16 * 128 ; Inlcude the first 128 tiles

The big problem with this is that there is a gap between both "halves", which is not ideal... so I prefer the other solution, which is to use a script that flips bit 7 of the tilemap data. If you need help with that, I can provide code fragments.

I don't like copying both halves separately, because that comes at a runtime cost, and I prefer to defer computations to compile-time when possible.

Last edited by ISSOtm (2020-04-27 09:33:18)

@issotm: i have downloaded superfamiconv. I do not find the option to offset map data. Could you help me on this, pls?

Aaaaaaaaaaaaaaaaaaaafrh: I got an old version where -T was « maximum number of tiles ». I have version v0.9.2 now with the option you described. Thank you again