const dA = 1, dB = 0.5;

var kill = 0.062775, feed = 0.031025;

​

//Change only when random points are applied.

var start = 1;

​

/*

Different seeds for different patterns.

kill: 0.0579 feed: 0.0227

kill: 0.06195 feed: 0.0449

kill: 0.062775 feed: 0.031025

kill: 0.058225 feed: 0.03755

kill: 0.055875 feed: 0.02232

kill: 0.0555 feed: 0.0291

kill: 0.0641 feed: 0.04677500

kill: 0.06095 feed: 0.04325000

*/

​

function setup(){

  createCanvas(400, 400);

  pixelDensity(1);

  colorMode(HSB);

  grid = [];

  next = [];

  for(var i = 0; i < width; i++){

    grid[i] = [];

    next[i] = [];

    for(var j = 0; j < height; j++){

      grid[i][j] = { a: 1, b: 0};

      next[i][j] = { a: 1, b: 0};

    }

  }

  for(var x = 0; x < start; x++){

    //Apply tempX and tempY to the loops for multiple diffusions.

    var tempX = floor(random(30, width -30));

    var tempY = floor(random(30, height -30));

    for(var k = 190; k < 211; k++){

      for(var l = 190; l < 211; l++){

        grid[k][l].b = 1;

      }

    }

  }

}

​

function draw(){

  background(255);

  for(var i = 1; i < width - 1; i++){

    for(var j = 1; j < height - 1; j++){

      var a = grid[i][j].a;

      var b = grid[i][j].b;

      //Uncomment the next two line for a full show of the different diffusions.

      //kill = map(i, 0, width, 0.055, 0.065);

      //feed = map(j, 0, height, 0.05, 0.02);

      next[i][j].a = a + (dA * laplace(true, i, j) - (a * b * b) + feed * (1 - a));

      next[i][j].b = b + (dB * laplace(false, i, j) + (a * b * b) - (kill + feed) * b);

    }

  }

  loadPixels();

  for(var k = 0; k < width; k++){

    for(var l = 0; l < height; l++){

      var index = (k + l * width) * 4;

      var c = 300-abs((next[k][l].a - next[k][l].b) * 255);

      pixels[index + 0] = c;

      pixels[index + 1] = c;

      pixels[index + 2] = c;

      pixels[index + 3] = 255;

    }

  }

  updatePixels();

  swap();

​

}

​

function swap(){

  var temp = grid;

  grid = next;

  next = temp;

}

​

function laplace(isA, i, j){

  var sum = 0;

  if(isA){

    sum += grid[i][j].a * -1;

    sum += grid[i - 1][j].a * 0.2;

    sum += grid[i][j - 1].a * 0.2;

    sum += grid[i + 1][j].a * 0.2;

    sum += grid[i][j + 1].a * 0.2;

    sum += grid[i - 1][j - 1].a * 0.05;

    sum += grid[i + 1][j - 1].a * 0.05;

    sum += grid[i - 1][j + 1].a * 0.05;

    sum += grid[i + 1][j + 1].a * 0.05;

  }else{

    sum += grid[i][j].b * -1;

    sum += grid[i - 1][j].b * 0.2;

    sum += grid[i][j - 1].b * 0.2;

    sum += grid[i + 1][j].b * 0.2;

    sum += grid[i][j + 1].b * 0.2;

    sum += grid[i - 1][j - 1].b * 0.05;

    sum += grid[i + 1][j - 1].b * 0.05;

    sum += grid[i - 1][j + 1].b * 0.05;

    sum += grid[i + 1][j + 1].b * 0.05;

  }

​

  return sum;

}