I've been working on an Advance Wars 1 hack which uses the CO Japanese sprites from Gameboy Wars 1.

However, there is one change I would like to make before I release the patch.

I want to change the background image (which appears at the title screen) and have the following image:


From: 1802 - Gameboy Wars Advance 1+2 (J)(Caravan).gba

replace:


From: 0263 - Advance Wars (E).gba


The problem is, I've never edited background images before and I've tried looking for the image in unzl.gba but I had no luck and couldn't find it in 'Tile layer pro'.  Is there a better software to edit background images or to even find the location of where the image is being stored?

what's the difference between the two, anyway? the only difference i see is the guy riding the parachute's hair color.

The tank color looks like its a slightly different shade (or maybe it's just me).

I think I just took the image a bit too soon while it was loading the image.  But both images use the same palette.



That's Olaf.  In the Japanese version, he has a white beard and wears a woolly hat.  He looks like Santa Claus to us Americans/Europeans so you can guess why his sprite got changed in the USA version.



So the image is compressed.  I was a bit unsure. 

Thanks for the information labmaster.  I should have thought to use loggings. 



That helps a lot Odin_Knight.  I better go and download the tools.  The one thing I don't understand is when you are editing the .dat data, will it make the necessary changes to the rom?  Or would I have to import it back in myself?

Thanks for the help everyone.  I report back some when today or tomorrow about my progress.   

there's something interesting that can be done with unLZ.

always when a GBA rom is opened by unLZ, it firstly analyses the rom, searching for possible compressed LZ data, based in pointers. when it finds, it creates a file called romname.gba.spr or something like that, and besides it create too a file called romname.gba.pal, which refers to possible palettes found.

but the program isn't totally free of bugs yet. the game can find compressed data of games like Gunstar Super Heroes or Metroid Zero Mission easily, but can't find the same ones of games like Castlevania Aria of Sorrow or Megaman Zero. and for all those games i mentioned, the compressed graphics are in LZ, pointed by a 3-byte pointer, the same mechanism.

the same thing happen with the palette searching method. it can't find the palettes always. so, a useful hint is to activate "black and white palette". this way, atleast you'll be able to see something, and not only totally black stuff.

coming back to the file romname.gba.spr, the program only create this file and the other one if it don't exists. so, do the following: open that file in a hexadecimal editor and take a look into the hexadecimal part. if you're familiar with GBA pointer tables, you'll see that it's exactly pointer table data, in inversed order just like most gba games.

so, if you activate the logging just like Odin_Knight and go get the offsets, just like that way:

LZ77UnCompWram: 0x0819f8fc,0x02000000 (VCOUNT=77)

get the hexadecimal value 0x0819F8FC and remove the first 0x08. it'll become that way: 19F8FC. that's exactly the offset where the compressed graphic is.

in a form extremely similar, you'll find one or more pointers with this value somewhere in the rom:
FCF819.

if that's the case, if you hack the file romname.gba.spr and put inside the file the pointer value above, you'll see exactly the same graphic that you probably couldn't see normally in unLZ. and this way you can extract, edit, reinsert, etc.

maybe you'll have palette problems editing this way, but anyway good luck.

Correct me if I'm wrong but vanilla vba should just be an official version of the emulator.

I'm getting there.  As I've mentioned before, the image I want to edit is in two parts. 

After using the Logging tool, I found this:


The two offsets that I need in order to get unlz.gba to load them are:

FCF81908 - Top Half of Image

AC271A08 - Bottom Half of Image

I'm only interested in the bottom half of the image where Olaf is located and too confirm the second offset is correct:




Now I got to find the compressed image offset in Gameboy Wars 1, extract the image and import it into AW1.  Then I can release the patch.  ^^

good job.

now, based with this, you can edit most compressed LZ graphics in GBA roms. and you don't need to know programming and technical stuff about how to compress/decompress in LZ and make a program to make it for you (as is needed for most cases).

with unLZ, you still can recompress the data and put it in other place of the rom. this way, you can avoid problems of compressed data that became too big compared to the original. one thing i think people does is use the free non-used space that is available in most GBA roms. in some games where the rom size is 8mb and they uses alotta LZ compression, i already found almost 2mb of non-used space. summary, if that rom has 8mb, the total space used is less than 7mb, and all that space can be freely used as free space for texts, graphics, splashes, etc.

that explains the reason most roms that way have intros from groups who ripped the roms (splashes). and if you find a rom with more than 60k of free space gathered in one place, better get only roms without intros. else, maybe you'll have problems. the free space you probably is going to use, can be probably the same one groups used for intros. and it can make the rom crash in a way.