Gfx tiles saved in Arcade Game roms

Question

I'm trying to see how are the tiles saved doing some reverse engineering using old roms gfx files (this example trying with snow bros arcade set one) .

This is what I know now :

• Each color point to a palette which can change (then when you change palette you change that color in tiles).

• Tiles have a 16x16 size.

I'm a little confused cause when I see the file in an hex editor . I don't know how many bytes are a pixel or how are they order to see the tile.

Any idea of how this works?

Answer 1

I've found the answer (at least at snowbros game):

tiles are saved in 128 bytes.

Being each byte 2 colors (4 bits per color (indexed of course)) and extructured this way:

Hex file:

Of course hex starts at 0 , but i think this is more visual , each celd is a byte (2 pixels).