noise.ts

import path from 'node:path'
import fs from 'node:fs/promises'

import { createNoise2D } from 'simplex-noise'
import { createCanvas, createImageData } from 'canvas'

const OUTPUT_PATH = path.join(__dirname, '../../web/public/noise.png')

/**
 * Creates a 200x200 canvas with a noise pattern.
 */
export function makeSomeNoise() {
  const noise2D = createNoise2D()

  const canvas = createCanvas(200, 200)
  const ctx = canvas.getContext('2d')
  const imageData = createImageData(200, 200)

  for (let x = 0; x < 200; x++) {
    for (let y = 0; y < 200; y++) {
      const cell = (x + y * 200) * 4

      // https://cmaher.github.io/posts/working-with-simplex-noise/
      const luminance = transform(noise2D(x, y), [-1, 1], [175, 255])

      imageData.data[cell] = luminance
      imageData.data[cell + 1] = luminance
      imageData.data[cell + 2] = luminance
      imageData.data[cell + 3] = luminance
    }
  }

  ctx.putImageData(imageData, 0, 0)

  return canvas.toBuffer()
}

async function main() {
  const png = makeSomeNoise()
  await fs.writeFile(OUTPUT_PATH, png)
}

// Start

if (require.main === module) {
  main()
    .then(() => {
      console.log(`Noise written to ${OUTPUT_PATH}`)
    })
    .catch((error) => {
      console.error(error)
      process.exit(1)
    })
}

/**
 * Transforms a value from one range to another.
 */
function transform(val: number, input: [number, number], output: [number, number]): number {
  const [inputMin, inputMax] = input
  const [outputMin, outputMax] = output

  return ((val - inputMin) / (inputMax - inputMin)) * (outputMax - outputMin) + outputMin
}