fixing newb problems

gistfile1.js

window.onload = ->
  img = new Image()
  img.src = '600.jpeg'
  img.onload = ->
    el = document.getElementById('stage')
    ctx = el.getContext('2d')
    el.setAttribute 'width', img.width
    el.setAttribute 'height', img.height

    ctx.drawImage img, 0, 0

    width = img.width
    height = img.height

    img_data = ctx.getImageData(0, 0, width, height)

    # color conversion and processing functions

    hue_to_rgb = (m1, m2, h) ->
      h += 1 if h < 0
      h -= 1 if h > 1
      return m1 + (m2 - m1) * h * 6 if h * 6 < 1
      return m2 if h * 2 < 1
      return m1 + (m2 - m1) * (2.0/3 - h) * 6 if h * 3 < 2
      return m1

    rgb_to_hsl = (rgbin) ->
      rgb = []
      for val in rgbin
        rgb.push val/255.0
      max = Math.max.apply(Math, rgb)
      min = Math.min.apply(Math, rgb)
      diff = max - min
      h = switch max
        when min then 0
        when rgb[0] then 60 * (rgb[1]-rgb[2]) / diff
        when rgb[1] then 60 * (rgb[2]-rgb[0]) / diff + 120
        when rgb[2] then 60 * (rgb[0]-rgb[1]) / diff + 240

      l = (max + min) / 2.0

      s = if max == min
        0
      else if l < 0.5
        diff / (2 * l)
      else
        diff / (2 - 2 * l)

      [h % 360, s * 100, l * 100]

    hsl_to_rgb = (hsl) ->

      h = hsl[0] / 360.0
      s = hsl[1] / 100.0
      l = hsl[2] / 100.0

      m2 = if l <= 0.5 then l * (s + 1) else l + s - l * s
      m1 = l * 2 - m2

      rgb = []
      rgb[0] = Math.round(hue_to_rgb(m1, m2, h + 1.0/3) * 0xff)
      rgb[1] = Math.round(hue_to_rgb(m1, m2, h) * 0xff)
      rgb[2] = Math.round(hue_to_rgb(m1, m2, h - 1.0/3) * 0xff)

      return rgb

    # return the rgba value of the pixel at x, y
    get_pixel = (x, y, type) ->
      index = (x + y * img_data.width) * 4
      if type == 'rgb'
        [img_data.data[index], img_data.data[index + 1], img_data.data[index + 2]]
      else
        [img_data.data[index], img_data.data[index + 1], img_data.data[index + 2], img_data.data[index +  3]]

    # set pixel at x, y to the rgba array passed in
    set_pixel = (x, y, color) ->
      index = (x + y * img_data.width) * 4
      for x in [0..3]
        img_data.data[index + x] = color[x]

    lighten = (x, y, amount) ->
      pixel_color = get_pixel(x, y, 'rgb')

      pixel_color[0] = Math.min 255, pixel_color[0] + amount
      pixel_color[1] = Math.min 255, pixel_color[1] + amount
      pixel_color[2] = Math.min 255, pixel_color[2] + amount
      pixel_color[3] = 255 # can't yet handle alpha
      set_pixel(x, y, pixel_color)


    desaturate = (x, y, percent) ->

    saturate = (x, y, percent) ->

    darken = (x, y, percent) ->

    for x in [0..img_data.width]
      for y in [0..img_data.height]
        lighten x, y, 255 * .1

    ctx.putImageData img_data, 0, 0 # re-render the image