local Screen = require("screen")
local sw, sh, iw, ih
local anim, frame, scrn

function _init()
  scrn = Screen:new("Rotate and zoom!", 10, 8)
  anim = image.load(_DIR .. "images/juggler.gif")
  trimanim()
  scrn:usepalette(anim[1])
  scrn:autocolor()
  sys.stepinterval(1000 / 30)
  frame = 0
  sw, sh = scrn:size()
  iw, ih = image.size(anim[1])
end
function _step(t)
  scrn:step(t)
  view.active(scrn.mainvp)
  frame = frame + 1
  if frame > #anim then
    frame = 1
  end
  local a = t / 1000
  local d = math.abs(math.sin(a * .3)) * iw * 4
  local x1, y1 = iw / 2 + math.sin(a + math.pi * 0.0) * d, ih / 2 - math.cos(a + math.pi * 0.0) * d
  local x2, y2 = iw / 2 + math.sin(a + math.pi * 0.5) * d, ih / 2 - math.cos(a + math.pi * 0.5) * d
  local x3, y3 = iw / 2 + math.sin(a + math.pi * 1.0) * d, ih / 2 - math.cos(a + math.pi * 1.0) * d
  local x4, y4 = iw / 2 + math.sin(a + math.pi * 1.5) * d, ih / 2 - math.cos(a + math.pi * 1.5) * d

  image.tri(anim[frame], sw / 2 - sh / 2, 0, sw / 2 + sh / 2, 0, sw / 2 + sh / 2, sh, x1, y1, x2, y2, x3, y3)
  image.tri(anim[frame], sw / 2 + sh / 2, sh, sw / 2 - sh / 2, sh, sw / 2 - sh / 2, 0, x3, y3, x4, y4, x1, y1)
  if input.hotkey() == "q" then
    sys.exit()
  end
end

function trimanim()
  view.active(scrn.rootvp)
  iw, ih = image.size(anim[1])
  local s = 1
  while s < math.min(iw, ih) do
    s = s * 2
  end
  while s > math.min(iw, ih) do
    s = s / 2
  end
  for i, frm in ipairs(anim) do
    local _frm = image.new(s, s, 8)
    gfx.cls()
    image.usepalette(frm)
    image.draw(frm, 0, 0, iw / 2 - s / 2, ih / 2 - s / 2, s, s)
    image.copy(_frm, 0, 0, 0, 0, s, s)
    image.copypalette(_frm)
    image.forget(frm)
    anim[i] = _frm
  end
end