Add Photo Scroller app

octopus/lib/octopus/apps/photo.ex

@@ -0,0 +1,43 @@
+defmodule Octopus.Apps.Photo do
+  use Octopus.App
+
+  alias Octopus.{Canvas, Image}
+  alias Octopus.Protobuf.InputEvent
+
+  @photo "monkey"
+  @fps 60
+
+  defmodule State do
+    defstruct [:photo, :time]
+  end
+
+  def name(), do: "Photo Scroller"
+
+  def init(_args) do
+    photo = Image.load(@photo)
+
+    :timer.send_interval(trunc(1000 / @fps), :tick)
+
+    {:ok, %State{photo: photo, time: 0}}
+  end
+
+  def handle_info(:tick, %State{} = state) do
+    canvas = Canvas.new((8+16)*10, 8)
+
+    dx = trunc((:math.sin(state.time)+1)/2*(state.photo.width-canvas.width))
+    dy = trunc((:math.sin(state.time/2)+1)/2*(state.photo.height-canvas.height))
+
+    pixel_coords = for x <- 0..(canvas.width-1), y <- 0..(canvas.height-1), do: {x, y}
+
+    canvas = Enum.reduce(pixel_coords, canvas, fn {x, y}, canvas ->
+      color = Canvas.get_pixel(state.photo, {x+dx, y+dy})
+      Canvas.put_pixel(canvas, {x, y}, color)
+    end)
+
+    canvas
+      |> Canvas.to_frame(drop: true)
+      |> send_frame()
+
+    {:noreply, %State{state | time: state.time + 1/@fps}}
+  end
+end