class ImageCompare

# File lib/image_compare.rb, line 4
def self.compare(test_img_blob, good_img_blob)
  new(test_img_blob, good_img_blob).compare
end

# File lib/image_compare.rb, line 8
def initialize(test_img_blob, good_img_blob)
  @test_img_blob = test_img_blob
  @good_img_blob = good_img_blob
end

# File lib/image_compare.rb, line 13
def compare
  diff = []

  good_img.height.times do |y|
    good_img.row(y).each_with_index do |pixel, x|
      diff << [x,y] unless pixel == test_img[x,y]
    end
  end

  changed_percent = diff.length.to_f / good_img.pixels.length

  puts "pixels (total):     #{good_img.pixels.length}"
  puts "pixels changed:     #{diff.length}"
  puts "pixels changed (%): #{changed_percent * 100}%"

  if diff.length > 0
    x, y = diff.map{ |xy| xy[0] }, diff.map{ |xy| xy[1] }

    test_img.rect(x.min, y.min, x.max, y.max, ChunkyPNG::Color.rgb(0,255,0))
    test_img.save('diff.png')
  end

  changed_percent
end

# File lib/image_compare.rb, line 42
def good_img
  @good_img ||= ChunkyPNG::Image.from_blob(@good_img_blob)
end

# File lib/image_compare.rb, line 38
def test_img
  @test_img ||= ChunkyPNG::Image.from_blob(@test_img_blob)
end