Codebrawl #2 Entry: “Pixelizing images with ChunkyPNG”

output.png

pixelize.rb

require 'rubygems'
require 'chunky_png'
include ChunkyPNG

class Pixelizer
  attr_reader :canvas
  
  def initialize(canvas, size=10)
    @canvas = canvas
    @size = size.to_i
    @rows = (@canvas.height.to_f / @size).ceil
    @columns = (@canvas.width.to_f / @size).ceil
  end
  
  # Fills each block with the average color of its pixels
  def pixelize
    blocks.each do |block|
      block.fill(block.average_color)
    end
    self
  end
  
  # An array of the blocks composing the canvas
  def blocks
    @blocks ||= [].tap do |blocks|
      @rows.times do |row|
        @columns.times do |column|
          blocks << Block.new(@canvas, @size * column, @size * row, @size, @size)
        end
      end
    end
  end
  
  class Block
    def initialize(canvas, x, y, width, height)
      @canvas = canvas
      @x0, @y0, @x1, @y1 = x, y, x + width, y + height
    end
    
    def average_color
      colors = []
      for x in @x0...@x1
        for y in @y0...@y1
          colors << Color.to_truecolor_bytes(@canvas[x, y]) if @canvas.include_xy?(x, y)
        end
      end
      Color.rgb *colors.transpose.map { |c| c.inject(:+) / c.size }
    end
    
    def fill(color)
      @canvas.rect(@x0, @y0, @x1, @y1, Color::TRANSPARENT, color)
    end
  end
end

input = Image.from_file('input.png')
output = Pixelizer.new(input).pixelize.canvas
output.save('output.png')