conway-game

README

Conway's Game

John Horton Conway sadly passed away on April, 11, 2020. Among so many contributions he also conceived the Game of Life ---here denoted as Conway's Game

This Go package is a personal tribute to his memory

Installation

To install the conway-game package execute:

$ go get github.com/clinaresl/conway-game

and a directory called github.com/clinaresl/conway-game will be created under the src/ folder of your $GOPATH.

To compile the program go to $GOPATH/src/github.com/clinaresl/conway-game and type:

$ go build

and the executable conway-game will be generated. You can test it with:

$ ./conway-game --version

To access the documentation of this package run godoc:

$ godoc -http "localhost:8080"

and access to the URL localhost:8080 with your favourite browser (hopefully Firefox)

Usage

conway-game provides various functionalities for generating animated GIF images which are stored in the file specified with --filename. It randomly locates an arbitrary number of living cells (specified with --population) over a grid of dimensions width and height (which are specified with the flags --width and --height respectively) and applies the rules of the Game of Life (Conway's Game) for the number of generations given in --generations, described in the Wikipedia as follows:

1. Any live cell with fewer than two live neighbours dies, as if by underpopulation.
2. Any live cell with two or three live neighbours lives on to the next generation.
3. Any live cell with more than three live neighbours dies, as if by overpopulation.
4. Any dead cell with exactly three live neighbours becomes a live cell, as if by reproduction.

It also provides the following functionalities:

• It is possible to specify the delay between frames (with --delay), and also the delay of the first frame (--delay0), so that the first one can become visible any amount of time.

• By default, each cell takes a pixel of the GIF image. It is possible, however, to apply any x/y aspect ratio to the image with --xratio/--yratio, which are not expected to be necessarily the same.

• It acknowledges various color models through --model. To get a complete overview of the different colour models use --help-model.

• Finally, to give a sense of evolution, it is also feasible to compute the average of colors of the same cell over an arbitrary number of consecutive generations with --average.

Examples

A number of examples of the different functionalities provided by this tiny package are given below

Aspect ratio

The most basic of all examples is given below:

./conway-game --filename test.gif --generations 100 --width 50 --height 50 
              --population 720 --xratio 10 --yratio 10 
              --model "gradient #000000:#00ff00:#00ff00"

which produces an old-fashioned image with big pixels, live cells shown in green and the background in black:

As an example of the possibility of modifying the aspect ratio, the following command:

./conway-game --filename test.gif --generations 300 --width 150 --height 150 
              --population 7500 --xratio 8 --yratio 2 
              --model "gradient #000000:#ffff00:#ffff00"

modifies the aspect ratio so that cells are four times wider:

Gradient color model

Just by making the color of the first generation equal to the background and using a different color for the last frame, it is possible to create a fade-in effect with the color model gradient:

./conway-game --filename test.gif --generations 300 --width 300 --height 300 
             --population 25000 --xratio 2 --yratio 2 
             --model "gradient #000044:#000044:#ff0000"

Conversely, it is also possible to create a fade-out effect under the same color model just by inverting the second and third color as follows:

./conway-game --filename test.gif --generations 300 --width 300 --height 300 
             --population 25000 --xratio 2 --yratio 2 
             --model "gradient #000044:#ff0000:#000044"

But it is of course fine to move gradually between any arbitrary combinations of red, green and blue as shown below:

./conway-game --filename test.gif --generations 300 --width 300 --height 300 
              --population 25000 --xratio 2 --yratio 2 
              --model "gradient #000033:#ff0000:#ffff00"

Radial color model

The radial color model assigns a color to each cell according to its distance to a given center with a comma-separated list of coordinates in --model after the combination of colors. The following example colors those cells near the right center of the grid with colors closer to the second one, and cells far from it get colors closer to the third:

./conway-game --filename test.gif --generations 300 --width 300 --height 300 
              --population 10000 --xratio 2 --yratio 2 
              --model "radial #002222:#ff0000:#008888;150,150"

Of course, the center can be placed anywhere on the grid:

./conway-game --filename test.gif --generations 300 --width 300 --height 300 
              --population 10000 --xratio 2 --yratio 2 
              --model "radial #000000:#ffffff:#000044;100,150"

Averaging frames

It is also possible to compute the average color of the same cell over an arbitrary number of consecutive frames provided with --average. The effect is different depending on the color model used.

Under the gradient color model, those cells that live for a short period of time get a dimmed color before dissapearing. Those living for a long period of time increase their color until they reach their maximum and then gradually dissapear:

./conway-game --filename test.gif --generations 500 --width 100 --height 100 
              --population 3000 --xratio 5 --yratio 5
              --model "gradient #000033:#ff0000:#ffff00" --average 3
              --delay0 100 --delay 10 

To make the effect more noticeable, cells have been magnifying and they take 5x5 pixels each. Additionally, the animation has been slowed down with a delay of 10 hundreths of a second between each:

Under the radial color model, the color of each cell is upper bounded according to its distance to the given center. However, cells far from it can be coloured with those used near the center. The reason is that those cells living for a short period of time get a lower average, which is given the same color as those cells with a lower distance to the center.

./conway-game --filename test.gif --generations 500 --width 100 --height 100 
              --population 3000 --xratio 5 --yratio 5 
              --model "radial #000033:#ff0000:#ffff00;0,0" --average 3 
              --delay0 100 --delay 10 

Where the center has been located in the upper-left corner of the grid:

License

conway-game is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

conway-game is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with conway-game. If not, see http://www.gnu.org/licenses/.

Author

Carlos Linares Lopez carlos.linares@uc3m.es

Documentation

Overview

Conway's Game

John Horton Conway sadly passed away on April, 11, 2020 as another victim of COVID-19. Among so many contributions he also conceived the Game of Life ---here denoted as Conway's Game

This Go package is a personal tribute to his memory