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Speed Coded Cosine Dither

  1. d = document
  2. b = d.body
  3. wh = 300
  4. hs = wh / 2
  5. S = 1.5
  6. with(
  7.   b.appendChild(Object.assign(
  8.     d.createElement`canvas`, {
  9.       width: wh, height: wh
  10.     })).getContext`2d`) {
  11.  
  12.   canvas.style.transformOrigin = '0 0'
  13.   canvas.style.transform = `scale(${S})`
  14.   canvas.style.imageRendering = 'pixelated'
  15.  
  16.   fillStyle = 'gray'
  17.  
  18.   fillRect(0, 0, wh, wh)
  19.   shadowBlur = 80
  20.   shadowColor = 'black';
  21.   shadowOffsetY = 20
  22.   for (let i = 0; i < 70; i++) {
  23.     save()
  24.     translate(hs, hs)
  25.     rotate(i / 33)
  26.     scale(1 - i / 100, 1)
  27.     translate(-hs, -hs)
  28.     fillStyle = `hsl(${i << 2}, 50%, 50%)`
  29.     beginPath()
  30.     arc(hs, hs, hs * .8, 0, 7)
  31.     fill()
  32.     restore()
  33.     shadowColor = 'transparent'
  34.     shadowBlur = 0
  35.   }
  36.  
  37.   C = Object.assign(d.createElement`canvas`, {
  38.     width: wh, height: wh
  39.   }).getContext('2d')
  40.   C.drawImage(canvas, 0, 0);
  41.  
  42.   im = getImageData(0, 0, wh, wh);
  43.  
  44.   p = im.data
  45.   size = wh * wh * 4
  46.  
  47.   modd = Math.random() * 5550
  48.   for (let i = 0; i < size; i += 4) {
  49.     if (Math.random() < 0.0001) modd = Math.random() * 5550
  50.     M = Math.cos(i % modd) * 255
  51.     p[i] = M < p[i] ? 255 : 0;
  52.     p[i + 1] = M < p[i + 1] ? 255 : 0;
  53.     p[i + 2] = M < p[i + 2] ? 255 : 0;
  54.   }
  55.  
  56.   putImageData(im, 0, 0);
  57.   globalCompositeOperation = 'hard-light'
  58.   drawImage(C.canvas, 0, 0);
  59. }

Some speed-coded canvas stuff with a dither inspired by #genuary2022

snippet.zone ~ 2021-22 /// {s/z}