let n = 250; //number of particle

let noiseScale = 0.006; //noise scale;

let stroke_r = 80; // size of the "pen"

​

let img; // source image

let imgW = 1200;

let imgH = 950;

let imgScale = 0.5; // scaling down

let baseImg; // buffer canvas

let showImg = false;

​

let arr = []; // storing the centers of star rotation

​

// standard yellow

const R = 180;

const G = 165;

const B = 60;

​

​

​

function preload() {

  img = loadImage('sn.jpg');

}

​

​

function setup() {

  pixelDensity(1);

  createCanvas(imgW*imgScale, imgH*imgScale);

  background(0);

​

  //generate image

  baseImg = createGraphics(imgW*imgScale, imgH*imgScale);

  let arr = colorCompare(); // calculate the centers of rotation

  baseImg.background(0);

  renderImg(arr); // render the base image

​

  // initialize particles

  // for (let i = 0; i < n; i++) {

  //   particles.push(new Particle());

  // }

}

​

function draw() {

  background(0, 4);

  // tint(255, 10);

  // renderImg(stroke_r);

​

  // generate 5 particles every frame

  for (let i = 0; i < 5; i++) {

    particles.push(new Particle());

  }

  // if the number reaches limit, pop out the particles

  if (particles.length > n) {

    particles.splice(0,5);

  }

  // move the particles

  for(let i=0; i<particles.length; i++){

    let p = particles[i];

    p.calcforce();

    p.calcNoise();

    p.applyforce();

    p.display();

  }

}

​

// find pixels with smaller RGB distance to the standard yellow

function colorCompare() {

  for (let i = 0; i < imgW*imgScale; i ++) {

    for (let j = 0; j < imgH*imgScale; j ++) {

      let c = img.get(i/imgScale, j/imgScale);

      let r = c[0];

      let g = c[1];

      let b = c[2];

      let gbdiff = abs(r-g);

      if (gbdiff <= 20

          && r > R-20 && r < R+20

          && g > G-20 && g < G+20

          && b > B-30 && b < B+30) {

        arr.push([i,j]);

      }

​

    }

  }

  return arr;

}

​

​

// render the base image

function renderImg(arr) {

  baseImg.loadPixels();

  for (let spot of arr) {

    let x = spot[0];

    let y = spot[1];

    if (baseImg.pixels[(x + x*width) * 4] < 150) {

      for (let i = 0; i <= imgW*imgScale; i++) {

        for (let j = 0; j <= imgH*imgScale; j++) {

          let d = dist(x, y, i, j);

          if (d <= stroke_r) {

            baseImg.pixels[(i + j*width) * 4] += ((stroke_r-d)/stroke_r)*10;

            baseImg.pixels[(i + j*width) * 4+1] += ((stroke_r-d)/stroke_r)*10;

            baseImg.pixels[(i + j*width) * 4+2] += ((stroke_r-d)/stroke_r)*10;

          }

        }

      }

    }

  }

  baseImg.updatePixels();

​

  if (showImg == true) {

    image(baseImg, 0, 0);

  }

}

​

function keyPressed() {

  if (key == "i" || key == "I") {

    showImg = !showImg;

  }

}

​