Bangkok

Bangkok reads chess game descriptions and re-play the games. Notice of events (moves, captures, checks, etc.) are sent to a listener. Bangkok comes with a listener that generates a MIDI file. In other words, the chess game is turned into music.

Bangkok originated as the code for an art project by Tom Peak <[email protected]>.

The Web site of Bangkok is (bangkok.rubyforge.org). The RubyForge project page is rubyforge.org/projects/bangkok, where the latest version of bangkok may be downloaded. Bangkok is also available as a RubyGem.

Recent Changes

0.1.2

GameListener#move outputs two notes for a move and sets CC_PORTAMENTO_TIME so there is a glide from the first note to the second. The total length of the two ntoes is proportional to the distance the piece travels. The first note is short (a 32nd note), and the second takes up the rest of the time, thus allowing the portamento to have its effect.
GameListener#move also outputs multiple volume and pan values, moving smoothly from the original to the new value for the duration of the move’s notes.
New Square.at method returns a ready-made Square. Since they’re immutable, this reduces the number of objects that need to be created.
More tests.

0.1.1

Fixed bugs in the bin/bangkok script.
Implemented the -c command line argument.
Fixed a bug in the GameListener that prevented the MIDI file from being output.
Added parsing of the config file to GameListener.

Dependencies

The MIDI generation portion of Bangkok requires midilib 0.8.4 or later. If you install Bangkok as a RubyGem, it will fetch and install midilib for you.

The test suite in the tests directory requires the testing framework TestUnit, which comes with Ruby 1.8 and later and can also be found in the Ruby Application Archive (raa.ruby-lang.org).

To rebuild the gem or RDocs or run the tests easily, you can use the Rakefile which requires Rake (rake.rubyforge.org).

Installation

RubyGems Installation

To install Bangkok as a gem, type

% gem install bangkok

You may need root privileges to install the gem.

Manual Installation

After downloading and expanding the archive, you can install Bangkok with the command

% ruby install.rb

(or)

% ruby install.rb --install-dir=my_directory

You may need root privileges to install Bangkok.

Testing

% rake test

runs all of the tests in the test directory.

Overview

Bangkok replays a chess game. It reads chess game .pgn files. Interesting events during each game (moves, captures, checks, etc.) are sent to a listener.

Bangkok comes with a GameListener that creates a MIDI sequence. The listener is given to a ChessGame object, which then reads a .pgn file, creates a board, gives the moves to the board so it can move the pieces, and tells the listener when the game is over. At that time, the GameListener writes the MIDI sequence out to a MIDI file.

How to Use

From the command line

Here is how to generate a MIDI file from a chess match file, using the built-in GameListener. (This command line is awkward, and needs to get simpler.)

% bangkok [-c my_program_changes.rb] chess_game_file.pgn

Running that command creates the MIDI file chess_game_file.mid. The optional configuration file my_program_changes.rb lets you change the default program numbers used for each of the pieces. See examples/program_changes.rb for an example file.

For example, to run bangkok on the chess game in the examples directory, type

% bangkok examples/game.pgn

Example Scripts and Files

Here are short descriptions of each of the files found in the examples directory.

examples/announcer.rb creates a new listener that “announces” the game by printing some descriptive text for everything that happens during the game.
examples/game.pgn is an example chess match.
examples/program_changes.rb is an example configuration file that shows you how to change the default program change values. The values in this file are the same as the default values used by GameListener.

The Code

Only one class has anything to do with MIDI at all: GameListener. The rest of the classes in Bangkok know only about chess moves. This separation allows you to use Bangkok for your own nefarious chess-related purposes, whether musical or un-.

GameListener creates a MIDI sequence from the chess game’s moves. When a piece moves, MIDI notes are generated and a few controller values are set. Any listener you write must implement the methods

start_game(io)
end_game
move(piece, from_square, to_square)
capture(attacker_piece, loser_piece)
check
checkmate
pawn_to_queen(pawn)

For each move, the GameListener generates three sets of MIDI events: one for the move start, one for a point halfway between the start and the destination, and one for the destination. GameListener#midi_for_position creates a pan value (left = queenside, right = kingside), a volume value (max = center of board, min = top and bottom of board), and a quarter note. The note is from a C scale, where the low C = the color’s home rank and the high C = the opposite color’s home rank.

SPEAKER    midi 1 - 8    SPEAKER (black)

   low
    ^
    |
   high
  volume
    |
    v
   low

    <---- panning ---->

SPEAKER    midi 9 - 16    SPEAKER (white)

ChessGame takes a listener in its constructor and creates a Board. The method ChessGame#read_moves reads game data. Calling ChessGame#play moves the pieces, which in turn sends messages to the listener so it can react. See bin/bangkok and examples/announcer.rb for examples of how to use a ChessGame object.

Board creates pieces and hands moves to pieces. It tells the listener about things like captures and castles.

A Square represents a location on a Board.

A Piece has a color and a Square. It tells the listener about its moves. Subclasses of Piece such as Queen and Knight override Piece#could_perform_move, which checks to see if that piece could move from its current position to the move’s destination square. could_perform_move is called by the Board to determine which piece on the board needs to be moved.

A Move has a color, a destination square, an optional starting rank or file, and optional modifiers such as check or capture. A castle Move has no destination square (the Board moves the pieces).

Resources

The Ruby Web site (www.ruby-lang.org/en/index.html) contains an introduction to Ruby, the Ruby Application Archive (RAA) at raa.ruby-lang.org, and pointers to more information.

_Programming Ruby, The Pragmatic Programmer’s Guide_, by David Thomas and Andrew Hunt, is a well-written and practical introduction to Ruby. Its Web page at www.rubycentral.com/book also contains a wealth of Ruby information. Though the book is available online, I encourage you to purchase a copy of the second edition, available at pragmaticprogrammer.com/titles/ruby/.

midilib’s home is midilib.rubyforge.org.

To Do

:include: TODO

Support

Visit the forums, bug list, and mailing list pages at rubyforge.org/projects/bangkok
Send email to Jim Menard at [email protected]
Ask on the ruby-talk mailing list

Administrivia

Author: Jim Menard ([email protected])
License: Distributed under the same license as Ruby.

Copying

Bangkok is copyrighted free software by Jim Menard and is released under the same license as Ruby. See the Ruby license at www.ruby-lang.org/en/LICENSE.txt.

Bangkok may be freely copied in its entirety providing this notice, all source code, all documentation, and all other files are included.

Warranty

This software is provided “as is” and without any express or implied warranties, including, without limitation, the implied warranties of merchantability and fitness for a particular purpose.