Yu-Gi-Oh! Forbidden Memories Background Image Extractor

This is a utility designed to extract background images out of the game in DDS format.

Currently it only supports version SLUS-01411.

Currently it can only extract the basic background images found during the campaign mode.

TODO list

• add version detection and support for other versions

• maybe look into extracting other images and content

• maybe add repacking support

How to use

• Extract WA_MRG.MRG out of the disc image

• In the OS shell launch the app with following arguments: YGOFM-BGEx WA_MRG.MRG BGIndex where BGIndex is the number of the background you wish to extract

• If you wish to not untile the image, append 0 at the end, like this: YGOFM-BGEx WA_MRG.MRG BGIndex 0

How does it work

LBA calculation

The magic can be found within the calclba function.

The game stores its data in LBAs, meaning each data block is aligned to 0x800 bytes.

Backgrounds in WA_MRG.MRG start at LBA 0x21D5 for the US version of the game and may vary across regions.

These LBAs are hardcoded during compile time in the game executable, so it will differ per each region/variant of the game.

The function responsible for calculating LBAs for these background images can be found at offset 0x8002DF2C of the game executable.

Keep in mind that due to the odd way of calculating LBAs there are repeated images despite having different indicies.

Image conversion

Most of these images are stored in 256 color paletized format, with some being 16 colors.

PS1 palette is in RGB555 format, with the 15th bit being the "special transparency bit".

The tool converts them to a raw DDS ARGB image without any data loss.