Drawing on canvas and getting an URI

gistfile1.txt

class Smile.Utils.MarkImageDrawer
  constructor: (@mark, @canvas) ->
    @margin = 4
    @backgroundColor = '#338e07'
    @foregroundColor = '#fff'
    @width = 40
    @height = 60

  # Public: Draws a Mark in the buffer.
  #
  # Returns a String with a base64-encoded data url.
  draw: ->
    @canvas.width = @width
    @canvas.height = @height
  
    ctx = @canvas.getContext('2d')
    ctx.fillStyle = @backgroundColor
    ctx.fillRect 0, 0, @width, @height
  
    ctx.strokeStyle = ctx.fillStyle = @foregroundColor
    ctx.lineWidth = 2
    ctx.strokeRect 1, 1, @width - 2, @height - 2
    ctx.strokeRect 5, 5, @width - 10, @height - 10

    ctx.font = 'bold 12pt sans-serif'
    numberOffset = switch @mark.km.toString().length
                   when 2 then 10
                   when 1 then 15
                   else 7
  
    ctx.fillText @mark.sigla, 9, 25
    ctx.fillText @mark.km, numberOffset, 45

    @canvas.toDataURL()