ROM Hack GBC Graphic Editing

[sfg]

Hi,

I want to change the graphics for two GBC games (specifically Heroes of Might Magic 1 & 2). I fooled around in Tile Layer Pro for some time, but I don't think I'll be able to figure this stuff out for myself.
So, is there an easier way of finding which graphic is which, besides going through them tile by tile? Maybe with the help of an emulator (VBA has some sort of map viewer for example) ?
For the colors, can Tile Layer Pro show the colors that are actually used in the game? When I open a rom it shows only blue, green, white and blue. Having it show the actual colors would also help with finding the right graphics. If that's not possible, then how can I change the colors? This thing really puzzles me more than finding the graphics, which I suppose I could do with some patience.

 

[FAST6191]

I am not much of a GB/GBC hacker but the tools and techniques do carry across so hopefully I can answer your question.

On older systems "brute force" is the only truly simple way, tile/map/BG viewers tend to focus on the RAM that is assigned to video memory and while you can often snatch ram values and search for them in rom that is a bit crude (compression does kind of exist on the GB/GBC but nowhere near as often as the GBA and beyond and you likely have to account for data arrangement). After that you are more or less stuck with assembly level hacks although on the scale of things you can get away without knowing a great deal here.

http://nocash.emubase.de/pandocs.htm is the equivalent of the no$gba specs for the GB and GBC albeit not quite as in depth.

http://www.romhacking.net/?category=&P...itle=&desc= has a slew of tools.
http://www.romhacking.net/?category=&P...itle=&desc= has a bunch of guides, many are good but http://www.romhacking.net/docs/32/ is more or less directly what you want (A title screen hack is not all that different to a sprite hack or a background hack). It might also be worth skipping across to the SNES or GBA as the techniques will share a fair amount of similarity, indeed there is a great GBA graphics finding doc http://www.romhacking.net/docs/361/ .

As for colours that is a standard thing for most consoles most of the time- the graphics are somewhat similar to the paint by numbers stuff you might have done as a kid and as such most tile editors will just offer up a few base colours (I detailed it for the DS/GBA here: http://gbatemp.net/index.php?showtopic=45360 and the pandocs link above details GB and GBC hardware specifics). Assuming you do not want to change the available colours then it is easy enough to grab the palette from the memory of the rom (not sure what tile layer pro can use for GBC but finding an emulator to generate one should not be hard), if you want to edit available colours you will need to find the palette in the rom, the snatch from ram and search rom technique works quite well, if not it is a simple tweak on the finding graphics assembly hacks.
Note this fact is (ab)used by many games to vary monsters with limited memory and/or design (even on the PC versions of heroes it was somewhat evident in the creature upgrade paths) so be aware when changing things.