// Note that it is possible to randomly get a boring rug. Just press play again until you get a nice one!

​

// Read about the Persian rug algorithm; https://archive.bridgesmathart.org/2005/bridges2005-9.pdf

​

// Learn more here: https://github.com/kfahn22/Persian-Rug

​

// To learn more about recursion, watch Daniel Shiffman's Recursion Coding Challenge

// https://thecodingtrain.com/challenges/77-recursion

​

// Based on this Processing sketch (https://github.com/kfahn22/Persian-Rug/blob/main/sketch.pdez), which is adapted from https://stackoverflow.com/questions/26226531/persian-rug-recursion

​

// I am using the method for choosing colors from Dr. Eric Gossett https://www.youtube.com/watch?v=0wfPlzPvZiQ1

​

let n = 10; 

let sw = 2;

let palette = [];

let colorIndexArray = [];

​

function setup() {

  let canvasSize = Math.pow(2, n) + 1; // 257 x 257 for n = 8

  createCanvas(canvasSize, canvasSize);

  noLoop();

  colorMode(HSB);

​

  // Initialize the color index array

  colorIndexArray = Array(canvasSize)

    .fill()

    .map(() => Array(canvasSize).fill(0));

​

  // Draw border

  let s = floor(random(0, 255));

  let w = canvasSize - 1;

  drawBorder(0, 0, w, w, s);

​

  // Choose colors for the internal grid

  let shift = floor(random(1, 255));

  chooseColor(0, w, 0, w, shift);

}

​

function drawBorder(left, top, right, bottom, hueVal) {

  //let c = palette[colorIndex];

  stroke(hueVal, 100, 100);

  strokeWeight(sw);

  line(left, top, right, top); // Top

  line(left, bottom, right, bottom); // Bottom

  line(left, top, left, bottom); // Left

  line(right, top, right, bottom); // Right

}

​

function chooseColor(left, right, top, bottom, shift) {

  if (left < right - 1) {

    let newHue =

      (getIndex(colorIndexArray[left][top]) +

        getIndex(colorIndexArray[right][top]) +

        getIndex(colorIndexArray[left][bottom]) +

        getIndex(colorIndexArray[right][bottom]) +

        shift) %

      256;

​

    let midCol = floor((left + right) / 2);

    let midRow = floor((top + bottom) / 2);

​

    // Draw middle lines

    stroke(newHue, 100, 100);

    strokeWeight(sw)

    line(left + 1, midRow, right - 1, midRow); // Horizontal

    line(midCol, top + 1, midCol, bottom - 1); // Vertical

​

    // Update color index array

    colorIndexArray[midCol][midRow] = newHue;

​

    // Recursive calls

    chooseColor(left, midCol, top, midRow, shift);

    chooseColor(midCol, right, top, midRow, shift);

    chooseColor(left, midCol, midRow, bottom, shift);

    chooseColor(midCol, right, midRow, bottom, shift);

  }

}

​

function getIndex(colorIndex) {

  // Directly use the color index from the array

  return colorIndex;

}

​

function mousePressed() {

  save("rug.jpg");

}

​