Fix bugs in circle and line rasterizing.

lib/vivid.ex

@@ -1,2 +1,18 @@
 defmodule Vivid do
+
+  def example do
+    polygon = [{1,1}, {1,4}, {4,4}, {4,1}]
+      |> Enum.map(fn {x,y} -> Vivid.Point.init(x,y) end)
+      |> Vivid.Polygon.init
+
+    line = [{9,1}, {1,9}]
+      |> Enum.map(fn {x,y} -> Vivid.Point.init(x,y) end)
+      |> Vivid.Line.init
+
+    Vivid.Frame.init(10,10)
+      |> Vivid.Frame.push(polygon, 1)
+      |> Vivid.Frame.push(line, 1)
+      |> Vivid.Frame.puts
+  end
+
 end

lib/vivid/frame.ex

@@ -74,15 +74,15 @@ defmodule Vivid.Frame do
       ...> |> Vivid.Frame.push(circle, 1)
       ...> |> Vivid.Frame.to_string
       "...........\n" <>
-      ".....X.....\n" <>
-      "..X.....X..\n" <>
+      "....XXX....\n" <>
+      "..XX...XX..\n" <>
       "..X.....X..\n" <>
       ".X.......X.\n" <>
       ".X.......X.\n" <>
       ".X.......X.\n" <>
       "..X.....X..\n" <>
-      "..X.....X..\n" <>
-      ".....X.....\n"
+      "..XX...XX..\n" <>
+      "....XXX....\n"
 
       iex> line = Vivid.Line.init(Vivid.Point.init(0,0), Vivid.Point.init(50,50))
       ...> Vivid.Frame.init(5,5)
@@ -97,9 +97,13 @@ defmodule Vivid.Frame do
   def push(%Frame{buffer: buffer, colour_depth: c, width: w}=frame, shape, colour) when colour <= c do
     points = Vivid.Rasterize.rasterize(shape)
     buffer = Enum.reduce(points, buffer, fn(point, buffer) ->
+      if point_inside_bounds?(point, frame) do
         x = point |> Point.x
         y = point |> Point.y
         List.replace_at(buffer, (x * w) + y, colour)
+      else
+        buffer
+      end
     end)
     %{frame | buffer: buffer}
   end
@@ -143,4 +147,10 @@ defmodule Vivid.Frame do
   defp allocate_buffer(size) do
     Enum.map((1..size), fn(_) -> 0 end)
   end
+
+  defp point_inside_bounds?(%Point{x: x}, _frame) when x < 0, do: false
+  defp point_inside_bounds?(%Point{y: y}, _frame) when y < 0, do: false
+  defp point_inside_bounds?(%Point{x: x}, %Frame{width: w}) when x >= w, do: false
+  defp point_inside_bounds?(%Point{y: y}, %Frame{height: h}) when y >= h, do: false
+  defp point_inside_bounds?(_point, _frame), do: true
 end

lib/vivid/rasterize/circle.ex

@@ -1,5 +1,5 @@
 defimpl Vivid.Rasterize, for: Vivid.Circle do
-  alias Vivid.{Circle, Point}
+  alias Vivid.{Circle, Point, Polygon, Rasterize}
   import :math, only: [pow: 2, sqrt: 1]
 
   @moduledoc """
@@ -19,14 +19,18 @@ defimpl Vivid.Rasterize, for: Vivid.Circle do
       iex> Vivid.Circle.init(Vivid.Point.init(5,5), 4)
       ...> |> Vivid.Rasterize.rasterize
       MapSet.new([
-        %Vivid.Point{x: 1, y: 5}, %Vivid.Point{x: 2, y: 2},
+        %Vivid.Point{x: 1, y: 4}, %Vivid.Point{x: 1, y: 5},
+        %Vivid.Point{x: 1, y: 6}, %Vivid.Point{x: 2, y: 2},
+        %Vivid.Point{x: 2, y: 3}, %Vivid.Point{x: 2, y: 7},
         %Vivid.Point{x: 2, y: 8}, %Vivid.Point{x: 3, y: 2},
         %Vivid.Point{x: 3, y: 8}, %Vivid.Point{x: 4, y: 1},
         %Vivid.Point{x: 4, y: 9}, %Vivid.Point{x: 5, y: 1},
         %Vivid.Point{x: 5, y: 9}, %Vivid.Point{x: 6, y: 1},
         %Vivid.Point{x: 6, y: 9}, %Vivid.Point{x: 7, y: 2},
         %Vivid.Point{x: 7, y: 8}, %Vivid.Point{x: 8, y: 2},
-        %Vivid.Point{x: 8, y: 8}, %Vivid.Point{x: 9, y: 5}
+        %Vivid.Point{x: 8, y: 3}, %Vivid.Point{x: 8, y: 7},
+        %Vivid.Point{x: 8, y: 8}, %Vivid.Point{x: 9, y: 4},
+        %Vivid.Point{x: 9, y: 5}, %Vivid.Point{x: 9, y: 6}
       ])
   """
 
@@ -35,16 +39,20 @@ defimpl Vivid.Rasterize, for: Vivid.Circle do
     y_center  = point |> Point.y
     r_squared = pow(radius, 2)
 
-    Enum.reduce(0-radius..radius, MapSet.new, fn (x, points) ->
+    {points0, points1} = Enum.reduce(0-radius..radius, {[], []}, fn (x, {points0, points1}) ->
       y  = sqrt(r_squared - pow(x, 2)) |> round
-
       x  = x_center + x
-      y0 = y_center + y
-      y1 = y_center - y
-
-      points
-      |> MapSet.put(Point.init(x, y0))
-      |> MapSet.put(Point.init(x, y1))
+      y0 = y_center - y
+      y1 = y_center + y
+      points0 = [ Point.init(x, y0) | points0 ]
+      points1 = [ Point.init(x, y1) | points1 ]
+      {points0, points1}
     end)
+
+    points1 = points1 |> Enum.reverse
+
+    points0 ++ points1
+    |> Polygon.init
+    |> Rasterize.rasterize
   end
 end

lib/vivid/rasterize/line.ex

@@ -36,14 +36,18 @@ defimpl Vivid.Rasterize, for: Vivid.Line do
 
   """
   def rasterize(%Line{}=line) do
+    origin = line |> Line.origin
     dx = line |> Line.x_distance
     dy = line |> Line.y_distance
 
     steps = choose_largest_of(abs(dx), abs(dy))
+
+    if steps == 0 do
+      MapSet.new([origin])
+    else
       x_increment = dx / steps
       y_increment = dy / steps
 
-    origin = line |> Line.origin
 
       points = MapSet.new([origin])
       current_x = origin |> Point.x
@@ -51,6 +55,7 @@ defimpl Vivid.Rasterize, for: Vivid.Line do
 
       reduce_points(points, steps, current_x, current_y, x_increment, y_increment)
     end
+  end
 
   defp reduce_points(points, 0, _, _, _, _), do: points