let next;

let dA = 1;

let dB = 0.5;

let feed = 0.055;

let k = 0.062;

​

function setup() {

  createCanvas(200, 200);

  pixelDensity(1);

  grid = [];

  next = [];

  for (let x=0; x<width;x++){

    grid[x] = [];

    next[x] = [];

    for (let y=0; y<height; y++){

      grid[x][y] = {a:1, b:0};

      next[x][y] = {a:1, b:0};

    }

  }

  for (let i=100; i<110; i++){

    for (let j=100; j<110; j++){

      grid[i][j].b = 1;

    }

  }

}

​

function draw() {

  background(51);

  for (let x=1; x<width-1;x++){

    for (let y=1; y<height-1; y++){

      let a = grid[x][y].a;

      let b = grid[x][y].b;

      next[x][y].a = a + dA * 

                     laplaceA(x,y) - 

                     a * b * b +

                     feed * (1 - a);

      next[x][y].b = b + dB * 

                     laplaceB(x,y) + 

                     a * b * b -

                     (k + feed) * b;

    }

  }

  loadPixels();

  for (let x=1; x<width-1;x++){

    for (let y=1; y<height-1; y++){

      let c = color(255,0,100);

      let pix = (x+y*width)*4;

      pixels[pix] = floor(next[x][y].a*255);

      pixels[pix+1] = 0

      pixels[pix+2] = floor(next[x][y].b*255);

      pixels[pix+3] = 255;

    }

  }

  updatePixels();

  swap();

}

​

function laplaceA(x, y){

  let sumA = 0;

  sumA += grid[x][y].a * -1;

  sumA += grid[x-1][y].a * 0.2;

  sumA += grid[x+1][y].a * 0.2;

  sumA += grid[x][y-1].a * 0.2;

  sumA += grid[x][y+1].a * 0.2;

  sumA += grid[x-1][y-1].a * 0.05;

  sumA += grid[x+1][y-1].a * 0.05;

  sumA += grid[x+1][y+1].a * 0.05;

  sumA += grid[x-1][y+1].a * 0.05;

​

  return sumA;

}

​

function laplaceB(x, y){

  let sumB = 0;

  sumB += grid[x][y].b * -1;

  sumB += grid[x-1][y].b * 0.2;

  sumB += grid[x+1][y].b * 0.2;

  sumB += grid[x][y-1].b * 0.2;

  sumB += grid[x][y+1].b * 0.2;

  sumB += grid[x-1][y-1].b * 0.05;

  sumB += grid[x+1][y-1].b * 0.05;

  sumB += grid[x+1][y+1].b * 0.05;

  sumB += grid[x-1][y+1].b * 0.05;

​

  return sumB;

}

​

function swap(){

  let temp = grid;

  grid = next;

  next = temp;

}