gistfile1.rb

# Looping pixels!
Win = Gosu::Window.new(500, 500, false)
img = Gosu::Image.new(Win, filename)

# Show info of 1 pixel
p = img.get_pixel(100,100);
puts p.to_s

# loop and make grey
img.each{ |pixel| 
  averageG = ((pixel[0]+pixel[1]+pixel[2])/3)
  if (averageG)
  pixel[0]=averageG
  pixel[1]=averageG
  pixel[2]=averageG
}
img.save("output.png")