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GraveyardDuck

GraveyardDuck is a simple tool to decompress and recompress graphic files used in the old Famicom Disk System game Dracula II: Noroi no Fuuin, better known as Castlevania: Simon's Quest in the US.

It also works on Ai Senshi Nicol, Rampart and possibly other Konami games.

Compression Teardown

The above games use a very simple variant of run-length encoding (RLE), a simple compression scheme used in many early bitmap graphic formats.

Konami's RLE scheme can be expressed in a few simple rules:

  • if(n < 128) then write the following byte n times to the decompressed stream
  • if(n > 128) then write the following n bytes to the decompressed stream
  • if(n == 128) then write the following 256 bytes
  • if(n == 255) then terminate compression

In practice, the case of (n == 255) is almost impossible to encounter given the nature of the graphics this scheme is designed to compress.

Usage

Assuming the parameters:

  • FILENAME: The file into/from which data will be compressed/decompressed
  • POSITION: Offset where compressed data is located or will be stored
  • BLOCK: The file to which decompressed data will be written or from which it will be sourced

Decompression

graveduck.py -d [FILENAME] [POSITION] [BLOCK]

Compression

graveduck.py -c [FILENAME] [POSITION] [BLOCK]

Authors

Derrick Sobodash

Copyright

Copyright © 2012, 2013 Derrick Sobodash