Hitomezashi

one bit per grid line decides whether its row of dashes starts on the edge or one cell in, and the shifted lines join at the crossings into steps, staircases, and loops (hitomezashi)

Run

swift run --package-path Examples Example-Patterns-Hitomezashi

Source

Examples/Patterns/Hitomezashi/Sketch.swift

import Ollin

/// Hitomezashi stitching: every grid line carries a row of unit dashes, and one
/// bit per line decides whether its dashes start on the edge or one cell in.
/// The shifted lines join at the crossings into steps, staircases, and loops,
/// so a handful of coin flips reads as a woven cloth.
///
/// The design is a pure function of the seed, so it's computed once and held.
/// Both faces draw: the two-tone parity fill underneath (every hitomezashi
/// design two-colors exactly, region against region), the stitches over it.
/// A slow tide of noise leans the fill tones back and forth, so the cloth
/// breathes while the stitching holds still.
@main
final class HitomezashiStitches: Sketch {
    private var design: Hitomezashi?

    override func draw() {
        let design = self.design ?? {
            seed(11)
            let made = hitomezashi(in: bounds.inset(by: .all(60 * scale)),
                                   columns: 26, rows: 26)
            self.design = made
            return made
        }()

        background(Color(hex: 0x101A33))   // deep indigo cloth

        let low = Color(hex: 0x18264A)     // the sunken tone
        let high = Color(hex: 0x2C4A7F)    // the raised tone
        noStroke()
        for (cell, tone) in zip(design.grid.cells, design.parities) {
            let tide = signedNoise(cell.center.x * 0.002, cell.center.y * 0.002,
                                   time * 0.4) * 0.2
            let t = (tone ? 0.85 : 0.15) + tide
            fill(Color.mix(low, high, t))
            drawRect(cell.frame)
        }

        stroke(Color(hex: 0xF2E9DC))       // warm thread
        strokeWeight(5 * scale)
        strokeCap(.round)
        for dash in design.stitches {
            drawPolyline(dash.points, closed: false)
        }
    }
}