ComputerCraft MandelBrot renderer

--ComputerCraft MandelBrot renderer
--by Tomlacko
--pastebin UnZrcfER
-----------------------
--1 optional parameter: external monitor side
--Zoom by clicking on any spot
--move by arrow keys, zoom by num+/num-
--press space to save image as screenshot openable in paint program
-----------------------

function drawBar()
  m.setBackgroundColor(colors.black)
  m.setCursorPos(1, h)
  m.clearLine()
  m.write(" < " .. "ZoomFactor: " .. tostring(zoomspeed) .. " > ")
  m.setCursorPos(w-3,h)
  m.write("Exit")
end

function Screenshot()
  if isMonitor then
    print("Enter screenshot filename: ")
  else
    m.setCursorPos(1,h)
    m.setBackgroundColor(colors.black)
    m.clearLine()
    m.write("Enter screenshot filename: ")
  end
  name = read()
  if name=="" then
    if not isMonitor then
      drawBar()
      return true
    end
    print("Canceled...")
    return false
  end
  file = fs.open(name, "w")
  for y=1, h-1 do
    for x=1, w do
      if pixels[y][x]<10 then
        file.write(tostring(pixels[y][x]))
      elseif pixels[y][x]==10 then
        file.write("a")
      elseif pixels[y][x]==11 then
        file.write("b")
      elseif pixels[y][x]==12 then
        file.write("c")
      elseif pixels[y][x]==13 then
        file.write("d")
      elseif pixels[y][x]==14 then
        file.write("e")
      elseif pixels[y][x]==15 then
        file.write("f")
      end
    end
    file.write("\n")
  end
  file.close()
  if not isMonitor then
    drawBar()
    return true
  end
  print("Saved successfully...")
  return false
end

args = {...}
isMonitor = false
if args[1]=="top" or args[1]=="bottom" or args[1]=="left" or args[1]=="right" or args[1]=="front" or args[1]=="back" then
  m = peripheral.wrap(args[1])
  m.setTextScale(0.5)
  isMonitor = true
elseif args[1]~=nil then
  print("Invalid monitor side argument!")
  return
else
  m = term
end
w, h = m.getSize()

if m.isColor() then
  gamut = 16
else
  gamut = 2
end
colordiff = 8
maxiter = 512
midx = w/2
midy = h/2
zoom = math.min(w,h)/3
offX = -0.5
offY = 0
zoomspeed = 4
interupt = 5

pixels = {}
for y=1, h-1 do
  pixels[y] = {}
  for x=1, w do
    pixels[y][x] = "0"
  end
end

while true do
  m.setBackgroundColor(colors.black)
  m.clear()
  m.setBackgroundColor(colors.white)
  drawBar()
  skip = false
  for y=1, h-1 do
    for x=1, w do
      xm = x-midx
      ym = y-midy
      x0 = xm/zoom + offX
      y0 = (ym*1.5)/zoom + offY
      a = 0
      b = 0
      rx = 0
      ry = 0
      c = 0
      while (c<maxiter) and (rx*rx+ry*ry <= 4) do
        rx = a*a - b*b + x0
        ry = 2*a*b + y0
        a = rx
        b = ry
        c = c + 1
      end
      if gamut <= 2 then
        cl = (c%2)*32767 + 1
        m.setBackgroundColor(cl)
        pixels[y][x] = (c%2)*15
      else
        if c==1 or c == maxiter then
          cl = 15
        else
          cl = math.floor(c/colordiff+math.log(c)^2)%(gamut-1)
        end
        --cl = math.abs((c-1+gamut-1)%((gamut-1)*2)-(gamut-1))
        --print(math.pow(2,cl))
        m.setBackgroundColor(math.pow(2,cl))
        pixels[y][x] = cl
      end
      m.setCursorPos(x, y)
      m.write(" ")
    end
    if y%interupt==0 then
      os.startTimer(0.05)
      ev, s, xpos, ypos = os.pullEvent()
      if ev == "monitor_touch" or ev == "key" or ev == "mouse_click" or ev == "mouse_scroll" then
        skip = true
        break
      end
    end
    if skip then break end
  end




  while true do
    if skip then
      skip = false
    else
      ev, s, xpos, ypos = os.pullEvent()
    end
    if (not isMonitor and (ev=="mouse_click" or ev=="mouse_scroll")) or (isMonitor and ev=="monitor_touch" and args[1]==s) then
      if ypos==h then
        if xpos>=w-3 then
          m.setBackgroundColor(colors.black)
          if isMonitor then
            m.setTextScale(1)
          end
          m.clear()
          m.setCursorPos(1,1)
          return
        elseif xpos <= 3 then
          zoomspeed = zoomspeed - 0.5
        elseif xpos > 3+12+#tostring(zoomspeed) and xpos <= 3+12+3+#tostring(zoomspeed) then
          zoomspeed = zoomspeed + 0.5
        end
        drawBar()
      else
        xpos = xpos - midx
        ypos = ypos - midy
        offX = offX + xpos/zoom
        offY = offY + (ypos*1.5)/zoom
        if (zoomspeed<0) or (zoomspeed>0 and ((ev=="mouse_click" and s==2) or (ev=="mouse_scroll" and s==1))) then
          zoom = zoom/math.abs(zoomspeed)
        elseif zoomspeed ~= 0 then
          zoom = zoom*math.abs(zoomspeed)
        end
        break
      end
    elseif ev=="key" then
      if s==200 then
        offY = offY - (midy/2)/zoom
        break
      elseif s==208 then
        offY = offY + (midy/2)/zoom
        break
      elseif s==203 then
        offX = offX - (midx/2)/zoom
        break
      elseif s==205 then
        offX = offX + (midx/2)/zoom
        break
      elseif (s==78 and zoomspeed>0) or (s==74 and zoomspeed<0) then
        zoom = zoom*math.abs(zoomspeed)
        break
      elseif (s==78 and zoomspeed<0) or (s==74 and zoomspeed>0) then
        zoom = zoom/math.abs(zoomspeed)
        break
      elseif s==57 then
        sleep(0.1)
        if Screenshot() then
          break --read moves page down
        end
      end
    end
  end
end