filter

Filters which cells to draw from a given quadrille q. It accepts the following types:

A value collection (Array or Set) Draws only the cells whose values are included in the collection. Example: drawQuadrille(q, { filter: [red, blue] })
A predicate function over the cell ((cell) => boolean) The function receives { row, col, value } and must return true to draw that cell. Example: drawQuadrille(q, { filter: ({ value }) => brightness(value) < 50 })

Arrow functions offer a compact syntax. For instance, the predicate
function (cell) {
  return brightness(cell.value) < 50;
}
becomes:
cell => brightness(cell.value) < 50;
You can also destructure to focus only on what you need:
({ value }) => brightness(value) < 50;

Example: Filtering by Value Collection#

(click on canvas and press any key to randomize q)

code

Quadrille.cellLength = 20;
Quadrille.outline = '#FF00FF';
Quadrille.outlineWeight = 1;
let q;
let yellow, blue, red;
let yellowBox, blueBox, redBox;
let values = [];

function setup() {
  createCanvas(600, 400);
  yellow = color('lemonchiffon');
  blue = color('skyblue');
  red = color('tomato');
  q = createQuadrille(30, 20).rand(200, yellow).rand(200, blue).fill(red);
  yellowBox = createCheckbox('Yellow', true).position(10, 10).changed(update);
  blueBox = createCheckbox('Blue', true).position(10, 30).changed(update);
  redBox = createCheckbox('Red', false).position(10, 50).changed(update);
  update();
}

function draw() {
  background(255);
  drawQuadrille(q, { filter: values });
}

function update() {
  values = [];
  yellowBox.checked() && values.push(yellow);
  blueBox.checked() && values.push(blue);
  redBox.checked() && values.push(red);
}

function keyPressed() {
  q.randomize();
}

The values array must contain references to the exact instances used to fill the quadrille. For example, if q was filled with the variable yellow = color('lemonchiffon'), then values must include that same variable, not a new color('lemonchiffon').

Example: Filtering by Predicate Value#

(click on canvas and press any key to randomize q)

code

Quadrille.cellLength = 20;
Quadrille.outline = '#FF00FF';
Quadrille.outlineWeight = 1;

let q;
let select;

const filters = {
  'All':    undefined,
  'Warm':   ({ value }) => red(value) > blue(value),
  'Dark':   ({ value }) => brightness(value) < 50,
  'Gothic': ({ value }) => saturation(value) < 20 && brightness(value) < 60
};

function setup() {
  createCanvas(600, 400);
  q = createQuadrille(30, 20);
  q.visit(({ row, col }) => q.fill(row, col, 
                                   color(random(255), random(255), random(255))));
  select = createSelect().position(10, 10);
  for (const label in filters) select.option(label);
}

function draw() {
  background(255);
  drawQuadrille(q, { filter: filters[select.value()] });
}

function keyPressed() {
  q.randomize();
}

The method q.visit(callback) iterates over all cells in row-major order, invoking callback({ row, col, value }) for each one. Use destructuring (e.g., { value }) when you only need part of the cell.

In JavaScript, for...in is used to iterate over object keys, typically for plain objects like filters:
for (const label in filters) {
  select.option(label);
}

Example: Filtering by Predicate Value, Row, and Column#

(click on canvas and press any key to randomize q)

code

Quadrille.cellLength = 20;
Quadrille.outline = '#FF00FF';
Quadrille.outlineWeight = 1;

const COLS = 30, ROWS = 20;
let q;
let select;

const filters = {
  'All':          undefined,
  'Even Rows':    ({ row }) => row % 2 === 0,
  'Left Half':    ({ col }) => col < COLS / 2,
  'Cool & Right': ({ value, col }) => blue(value) > red(value) && col >= COLS / 2,
  'Top Warm':     ({ value, row }) => red(value) > blue(value) && row < ROWS / 2
};

function setup() {
  createCanvas(600, 400);
  q = createQuadrille(COLS, ROWS);
  q.visit(({ row, col }) => q.fill(row, col,
                                   color(random(255), random(255), random(255))));
  select = createSelect().position(10, 10);
  for (const label in filters) select.option(label);
}

function draw() {
  background(255);
  drawQuadrille(q, { filter: filters[select.value()] });
}

function keyPressed() {
  q.randomize();
}

Syntax#

drawQuadrille(quadrille, { filter })

Parameters#

Param	Description
`filter`	Specifies which cells to draw. All cells are drawn if omitted or `undefined`. It can be: a value collection (`Array` or `Set`) checked by identity (`===`) against `cell.value` a cell-predicate function `({ row, col, value }) => boolean`