Glitchy image - OpenProcessing

mySketch
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/*
Glitchy image
​
A submission to the glitch art coding challenge.
​
Author:
  Jason Labbe
​
Site:
  jasonlabbe3d.com
*/
​
var img;
var spacing = 20;
var blocks = [];
var rgbIndex = 0;
var mod = 0;
var mult = 0;
​
function preload() {
  img = loadImage("toffee.jpg");
}
​
function setup() {
  createCanvas(windowWidth, windowHeight);
  frameRate(10);
  noStroke();
  
  img.loadPixels();
  
  for (let y = 0; y < img.height; y+=spacing) {
    for (let x = 0; x < img.width; x+=spacing) {
      block = img.get(x, y, spacing, spacing);
      blocks.push(block);
    }
  }
}
​
function draw() {
  background(0);
  
  translate(width / 2 - img.width / 2, height / 2 - img.height / 2);
  
  let offset = map(noise(frameCount * 0.1, 2000 + frameCount * 0.1), 0, 1, -1.5, 1.5);
  let columnCount = round(img.width / spacing) + offset;
  
  if (frameCount % 5 == 0) {
    glitch();
  }
  
  for (let i = 0; i < blocks.length; i++) {
    let x = int(i % columnCount) * spacing;
    let y = int(i / columnCount) * spacing;
    
    image(blocks[i], x, y);
    
    let r = 125;
    let g = 125;
    let b = 125;
    
    if (rgbIndex == 0) {
      r = ((frameCount + i) * mult) % mod;
    } else if (rgbIndex == 1) {
      g = ((frameCount + i) * mult) % mod;
    } else {
      b = ((frameCount + i) * mult) % mod;
    }
    
    fill(r, g, b, 150);
    rect(x, y, spacing, spacing);
  }
}
​
function mousePressed() {
  glitch();
}
​
function glitch() {
  frameCount = int(random(1000));
  rgbIndex = int(random(3));
  mod = int(random(255));
  mult = random(100);
}