Generate noise with canvas

noise.coffee

generateNoise = (opacity) ->
  return false  unless !!document.createElement("canvas").getContext
  canvas = document.createElement("canvas")
  ctx = canvas.getContext("2d")
  x = undefined
  y = undefined
  number = undefined
  opacity = opacity or .2
  canvas.width = 45
  canvas.height = 45
  x = 0
  while x < canvas.width
    y = 0
    while y < canvas.height
      number = Math.floor(Math.random() * 60)
      ctx.fillStyle = "rgba(" + number + "," + number + "," + number + "," + opacity + ")"
      ctx.fillRect x, y, 1, 1
      y++
    x++
  document.body.style.backgroundImage = "url(" + canvas.toDataURL("image/png") + ")"

generateNoise .1 # default opacity is .2

http://net.tutsplus.com/tutorials/javascript-ajax/how-to-generate-noise-with-canvas/