Convert an image to a 10x10 pixelated version

output.png

pixelize.rb

require 'chunky_png'

image = ChunkyPNG::Image.from_file('input.png')

image.height.times do |y|
  image.width.times do |x|
    # As we iterate over each pixel, copy only the color of the pixel
    # from the top left corner of this pixels 10x10 region
    #  e.g. the pixel at [69,17] will get set to the color from [60,10]
    image[x, y] = image[x / 10 * 10, y / 10 * 10]
  end
end

image.save('output.png')