Contents

require 'chunky_png'
include ChunkyPNG::Color

module Browsery
  class DiffImage

    def initialize(base_image, new_image)
      @base_image = ChunkyPNG::Image.from_file(base_image)
      @new_image = ChunkyPNG::Image.from_file(new_image)
      @diff_image = ChunkyPNG::Image.new(@base_image.width, @new_image.width, BLACK)
    end

    def calculate_changes
      diff = []

      @base_image.height.times do |y|
        @base_image.row(y).each_with_index do |pixel, x|
          unless pixel == @new_image[x,y]
            score = Math.sqrt(
              (r(@new_image[x,y]) - r(pixel)) ** 2 +
              (g(@new_image[x,y]) - g(pixel)) ** 2 +
              (b(@new_image[x,y]) - b(pixel)) ** 2
            ) / Math.sqrt(MAX ** 2 * 3)
            diff << score
          end
          @diff_image[x,y] = rgb(
            r(pixel) + r(@new_image[x,y]) - 2 * [r(pixel), r(@new_image[x,y])].min,
            g(pixel) + g(@new_image[x,y]) - 2 * [g(pixel), g(@new_image[x,y])].min,
            b(pixel) + b(@new_image[x,y]) - 2 * [b(pixel), b(@new_image[x,y])].min
          )
        end
      end

      total_pixels = @base_image.pixels.length
      diff_percentage = diff.empty? ? 0 : diff.inject {|sum, value| sum + value} / total_pixels
      puts "pixels (total):     #{total_pixels}"
      puts "pixels changed:     #{diff.length}"
      puts "image changed (%):  #{diff_percentage * 100} %"

      diff_percentage
    end

    def save_diff(diff_image)
      @diff_image.save(diff_image)
    end

  end
end

Version data entries

7 entries across 7 versions & 1 rubygems

Version	Path
browsery-0.5.5	lib/browsery/diff_image.rb
browsery-0.5.3	lib/browsery/diff_image.rb
browsery-0.5.2	lib/browsery/diff_image.rb
browsery-0.5.1	lib/browsery/diff_image.rb
browsery-0.5.0	lib/browsery/diff_image.rb
browsery-0.4.1	lib/browsery/diff_image.rb
browsery-0.4.0	lib/browsery/diff_image.rb