angelfan · March 21, 2016 02:03 · Oct 30, 2013 · Oct 30, 2013
diff --git a/si.rb b/si.rb
@@ -58,7 +58,7 @@ def calculate_threshold(img_fn)
    end
 
    #puts threshold
-   img = img.threshold(threshold)
+   img = img.threshold(threshold * 256)
    img.write(File.join(dir_name, "threshold_#{img_fn}"))
 
    result = Hash.new

diff --git a/si.rb b/si.rb
@@ -0,0 +1,105 @@
+require 'RMagick'
+
+$scale_size = 256.0
+$img_fn1 = ARGV[0]
+$img_fn2 = ARGV[1]
+$scale_size = ARGV[2].to_f if ARGV[2]
+
+def calculate_threshold(img_fn)
+   dir_name = File.dirname(img_fn)
+
+   img = Magick::Image.read(img_fn).first
+   img.scale!($scale_size, $scale_size)
+   img = img.quantize(256, Magick::GRAYColorspace)
+   img = img.negate(true)
+
+   # record negative image 
+   img.write(File.join(dir_name, "ng_#{img_fn}"))
+
+   rows = img.rows
+   cols = img.columns
+
+   pixels = img.export_pixels(0, 0, cols, rows, "I").map { |p| p / 256 }
+   total_pixels = pixels.size
+
+   # Calculate histogram
+   histogram = Array.new(256, 0)
+   pixels.each do |p| 
+      histogram[p] += 1 
+   end
+   #p histogram
+   sum = 0.0
+   256.times { |i| sum += i * histogram[i] }
+
+   sum_b = 0.0
+   w_b, w_f = 0, 0
+   max_cache = 0.0
+   threshold = 0
+
+   256.times do |t|
+      w_b += histogram[t]
+      next if 0 == w_b
+
+      w_f = total_pixels - w_b
+      break if 0 == w_f
+
+      sum_b += t * histogram[t]
+      m_b = sum_b / w_b
+      m_f = (sum - sum_b) / w_f
+
+      #puts "mb:#{m_b} mf:#{m_f} wb:#{w_b} wf:#{w_f}"
+
+      between = w_b * w_f * (m_b - m_f) ** 2
+
+      if between > max_cache
+         max_cache = between
+         threshold = t
+      end
+   end
+
+   #puts threshold
+   img = img.threshold(threshold)
+   img.write(File.join(dir_name, "threshold_#{img_fn}"))
+
+   result = Hash.new
+   result["threshold"] = threshold
+   result["bw_img"] = img
+
+   result
+end
+
+def hamming_dist(img_fn1, img_fn2)
+   img_result1 = calculate_threshold(img_fn1)
+   img_result2 = calculate_threshold(img_fn2)
+
+   img1 = img_result1["bw_img"]
+   pixels1 = img1.export_pixels(0, 0, img1.columns, img1.rows, "I").map { |p| p / 65535 }
+
+   img2 = img_result2["bw_img"]
+   pixels2 = img2.export_pixels(0, 0, img2.columns, img2.rows, "I").map { |p| p / 65535 }
+
+   hd = 0
+
+   difference_pixels = []
+   pixels1.each_index do |i|
+      pixel = pixels1[i] ^ pixels2[i] 
+      hd += pixel
+      difference_pixels[i] = pixel * 65535
+   end
+
+   [hd, difference_pixels]
+end
+
+result = hamming_dist($img_fn1, $img_fn2)
+hd = result[0]
+difference_rate = hd / $scale_size ** 2 * 100
+puts "Hamming distance: #{hd}"
+puts "Difference rate: #{difference_rate}%"
+
+if 0 != hd
+   d_img = Magick::Image.new($scale_size, $scale_size)
+   d_img.import_pixels(0, 0, $scale_size, $scale_size, "I", result[1])
+   fn1 = File.basename($img_fn1, File.extname($img_fn1))
+   fn2 = File.basename($img_fn2, File.extname($img_fn2))
+   d_img.write(File.join("#{fn1}_#{fn2}_diff_img.png"))
+end
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