output.png

pixelate.rb

require 'chunky_png'

module ChunkyPNG
  class Canvas
    module Pixelate
      # Pixelate image or part of the image
      # @param [Integer] block size for pixalating
      # @param [Integer] start x-coordinate for pixelating
      # @param [Integer] start y-coordinate for pixelating
      # @param [Integer] end x-coordinate for pixelating
      # @param [Integer] end y-coordinate for pixelating
      # @return [ChunkyPNG::Canvas] Itself, with pixelated applied
      def pixelate(block_size, x0 = 0, y0 = 0, x1 = self.width - 1, y1 = self.height - 1)
        half_block = block_size / 2

        x = x0
        y = y0

        while y <= y1
          while x <= x1
            x_color_point = min(x + half_block, width - 1)
            y_color_point = min(y + half_block, height - 1)

            x_end = min(x + block_size - 1, x1)
            y_end = min(y + block_size - 1, y1)

            color = self.get_pixel(x_color_point, y_color_point)
            self.rect(x, y, x_end, y_end, ChunkyPNG::Color::TRANSPARENT, color)
            x += block_size
          end

          x = x0
          y += block_size
        end

        self
      end

      private

      # internal simple function to calculate minimum of two values
      def min(a, b)
        return a if a < b
        return b
      end
    end

    # include module on Canvas
    include Pixelate
  end
end

image = ChunkyPNG::Image.from_file('input.png')
image.pixelate(10)
image.save('output.png')