Codebrawl #2 pixelater

output.png

solution.rb

require 'rubygems'
require 'chunky_png'

PIXEL_SIZE = 10

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

PIXELATED_width = (input.width.to_f/PIXEL_SIZE).ceil.to_i * PIXEL_SIZE
PIXELATED_height = (input.height.to_f/PIXEL_SIZE).ceil.to_i * PIXEL_SIZE
output = ChunkyPNG::Image.new(PIXELATED_width, PIXELATED_height, ChunkyPNG::Color::TRANSPARENT)

# divide into pixel grid
# deals with the remainder (i.e. output.width%PIXEL_SIZE) by cropping image afterwards
(PIXELATED_width/PIXEL_SIZE).times do |x|
  (PIXELATED_height/PIXEL_SIZE).times do |y|
    w = x*PIXEL_SIZE
    h = y*PIXEL_SIZE
    # get square of pixels
    begin
      pxl_space = input.crop(w,h,PIXEL_SIZE,PIXEL_SIZE)
    rescue ChunkyPNG::OutOfBounds
      pxl_space = input.crop(w,h,input.width-w,input.height-h)
    end
    # determine output pixel colour
    pxl_r = pxl_space.pixels.inject(0) { |s,v| s+=ChunkyPNG::Color.r(v) }/pxl_space.pixels.count
    pxl_g = pxl_space.pixels.inject(0) { |s,v| s+=ChunkyPNG::Color.g(v) }/pxl_space.pixels.count
    pxl_b = pxl_space.pixels.inject(0) { |s,v| s+=ChunkyPNG::Color.b(v) }/pxl_space.pixels.count
    # paint pixel
    output.rect(w, h, w+PIXEL_SIZE, h+PIXEL_SIZE, ChunkyPNG::Color::TRANSPARENT, ChunkyPNG::Color.rgb(pxl_r,pxl_g,pxl_b))
  end
end


# crop
output.crop!(0,0, input.width, input.height)
output.save('output.png')