My entry to the 2nd round of the CodeBrawl

output.png

Pixelize.rb

require 'chunky_png'
include ChunkyPNG::Color
include ChunkyPNG::Canvas::Drawing

input = ChunkyPNG::Image.from_file('input.png')
# Put your logic to averageize `image` here.

BLOCK_SIZE = 10

height = input.height
width = input.width

heightIterations = height / BLOCK_SIZE
widthIterations  = width / BLOCK_SIZE

canvas = ChunkyPNG::Canvas.new(width, height, WHITE)

def averageArray(array)
  return (array.inject { |sum, el| sum + el }.to_f / array.size).to_i
end

heightIterations.times do |y|
  widthIterations.times do |x|

    reds, greens, blues = [], [], []

    BLOCK_SIZE.times do |cy|
      BLOCK_SIZE.times do |cx|
        pixel = input[x * BLOCK_SIZE + cx, y * BLOCK_SIZE + cy]
        index = cy * BLOCK_SIZE + cx
        reds[index], greens[index], blues [index] = r(pixel), g(pixel), b(pixel)
      end
    end

    average = rgb(averageArray(reds), averageArray(greens), averageArray(blues))

    canvas.rect(x * BLOCK_SIZE, y * BLOCK_SIZE, (x+1) * BLOCK_SIZE, (y+1) * BLOCK_SIZE, average, average)
  end
end

# Save image
canvas.save('output.png')