2019: Day 8 Part 2

2019/day8/part2.rb

@@ -0,0 +1,86 @@
+# frozen_string_literal: true
+
+class Layer
+  attr_reader :width, :height, :pixels
+  def initialize(width, height, pixels)
+    @width = width
+    @height = height
+    @pixels = pixels
+  end
+
+  def get_pixel(r, c)
+    @pixels[r * @width + c]
+  end
+
+  def to_s
+    s = String.new
+    pixels.each_slice(@width) do |line|
+      s << line.join('')
+      s << "\n"
+    end
+    s
+  end
+
+  def to_tty
+    s = String.new
+    pixels.each_slice(@width) do |row|
+      line = row.map do |pixel|
+        case pixel
+        when 1
+          # Unicode full block
+          "\u2588"
+        when 0
+          ' '
+        else
+          raise ArgumentError, "Unexpected pixel value #{pixel}"
+        end
+      end
+      s << line.join('')
+      s << "\n"
+    end
+    s
+  end
+end
+
+class SpaceImage
+  attr_reader :width, :height, :data
+
+  def initialize(width, height, data)
+    @width = width
+    @height = height
+    @data = data.strip.chars.map(&:to_i)
+    raise ArgumentError, 'bad data' unless (@data.size % (@width * @height)).zero?
+  end
+
+  def layers
+    return @layers unless @layers.nil?
+
+    @layers = []
+    @data.each_slice(@width * @height) do |layer|
+      @layers << Layer.new(@width, @height, layer)
+    end
+    @layers
+  end
+
+  def render
+    pixels = []
+    @height.times do |r|
+      @width.times do |c|
+        pixel = get_pixel(r, c)
+        pixels << pixel
+      end
+    end
+    Layer.new(@width, @height, pixels)
+  end
+
+  def get_pixel(r, c)
+    layers.each do |layer|
+      pixel = layer.get_pixel(r, c)
+      return pixel if pixel != 2
+    end
+  end
+end
+
+input = File.read(File.join(__dir__, 'input'))
+img = SpaceImage.new(25, 6, input)
+puts img.render.to_tty