Add a sprite representation.

src/chalk/sprite.cr

@@ -0,0 +1,77 @@
+module Chalk
+  module Table
+    class Sprite
+      def initialize
+        @pixels = Hash(UInt8, UInt8).new(default_value: 0_u8)
+      end
+
+      def initialize(string, blank_char = ' ')
+        @pixels = Hash(UInt8, UInt8).new(default_value: 0_u8)
+        string.split("\n").each_with_index do |s, i|
+          break if i > 15
+          index = 0
+          byte = 0_u8
+          s.each_char do |char|
+            break if index > 7
+            bit = (char == blank_char) ? 0_u8 : 1_u8
+            byte |= (bit << (7 - index))
+            index += 1
+          end
+          @pixels[i.to_u8] = byte
+        end
+      end
+
+      def set_pixel(x, y)
+        raise "Invalid x-coordinate" if x > 7
+        raise "Invalid y-coordinate" if y > 15
+        x = x.to_u8
+        y = y.to_u8
+        char = @pixels.fetch y, 0_u8
+        char |= (1 << (7 - x))
+        @pixels[y] = char
+      end
+
+      def unset_pixel(x, y)
+        raise "Invalid x-coordinate" if x > 7
+        raise "Invalid y-coordinate" if y > 15
+        x = x.to_u8
+        y = y.to_u8
+        char = @pixels.fetch y, 0_u8
+        char &= ~(1 << (7 - x))
+        @pixels[y] = char
+      end
+
+      def toggle_pixel(x, y)
+        raise "Invalid x-coordinate" if x > 7
+        raise "Invalid y-coordinate" if y > 15
+        x = x.to_u8
+        y = y.to_u8
+        char = @pixels.fetch y, 0_u8
+        char ^= (1 << (7 - x))
+        @pixels[y] = char
+      end
+
+      def draw(io = STDOUT, blank_char = ' ', ink_char = 'x')
+        until_y = @pixels.keys.max?
+        return unless until_y
+        (0..until_y).each do |y|
+          row = @pixels.fetch y, 0_u8
+          pointer = 0b10000000
+          while pointer != 0
+            draw_pixel = (row & pointer) != 0
+            io << (draw_pixel ? ink_char : blank_char)
+            pointer = pointer >> 1
+          end
+          io << '\n'
+        end
+      end
+
+      def encode
+        if until_y = @pixels.keys.max?
+          return (0..until_y).map { |it| @pixels.fetch it, 0_u8 }
+        end
+        return [0_u8]
+      end
+    end
+  end
+end