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diff --git a/examples/box_in_scene.png b/examples/box_in_scene.png
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diff --git a/examples/find_obj.rb b/examples/find_obj.rb
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+#!/usr/bin/env ruby
+# -*- mode: ruby; coding: utf-8-unix -*- 
+
+# A Demo Ruby/OpenCV Implementation of SURF
+# See https://code.ros.org/trac/opencv/browser/tags/2.3.1/opencv/samples/c/find_obj.cpp
+require 'opencv'
+require 'benchmark'
+include OpenCV
+
+def compare_surf_descriptors(d1, d2, best, length)
+  raise ArgumentError unless (length % 4) == 0
+  total_cost = 0
+  0.step(length - 1, 4) { |i|
+    t0 = d1[i] - d2[i]
+    t1 = d1[i + 1] - d2[i + 1]
+    t2 = d1[i + 2] - d2[i + 2]
+    t3 = d1[i + 3] - d2[i + 3]
+    total_cost += t0 * t0 + t1 * t1 + t2 * t2 + t3 * t3
+    break if total_cost > best
+  }
+  total_cost
+end
+
+def naive_nearest_neighbor(vec, laplacian, model_keypoints, model_descriptors)
+  length = model_descriptors[0].size
+  neighbor = nil
+  dist1 = 1e6
+  dist2 = 1e6
+
+  model_descriptors.size.times { |i|
+    kp = model_keypoints[i]
+    mvec = model_descriptors[i]
+    next if laplacian != kp.laplacian
+    
+    d = compare_surf_descriptors(vec, mvec, dist2, length)
+    if d < dist1
+      dist2 = dist1
+      dist1 = d
+      neighbor = i
+    elsif d < dist2
+      dist2 = d
+    end
+  }
+
+  return (dist1 < 0.6 * dist2) ? neighbor : nil
+end
+
+def find_pairs(object_keypoints, object_descriptors,
+               image_keypoints, image_descriptors)
+  ptpairs = []
+  object_descriptors.size.times { |i|
+    kp = object_keypoints[i]
+    descriptor = object_descriptors[i]
+    nearest_neighbor = naive_nearest_neighbor(descriptor, kp.laplacian, image_keypoints, image_descriptors)
+    unless nearest_neighbor.nil?
+      ptpairs << i
+      ptpairs << nearest_neighbor
+    end
+  }
+  ptpairs
+end
+
+def locate_planar_object(object_keypoints, object_descriptors,
+                         image_keypoints, image_descriptors, src_corners)
+  ptpairs = find_pairs(object_keypoints, object_descriptors, image_keypoints, image_descriptors)
+  n = ptpairs.size / 2
+  return nil if n < 4
+
+  pt1 = []
+  pt2 = []
+  n.times { |i|
+    pt1 << object_keypoints[ptpairs[i * 2]].pt
+    pt2 << image_keypoints[ptpairs[i * 2 + 1]].pt
+  }
+
+  _pt1 = CvMat.new(1, n, CV_32F, 2)
+  _pt2 = CvMat.new(1, n, CV_32F, 2)
+  _pt1.set_data(pt1)
+  _pt2.set_data(pt2)
+  h = CvMat.find_homography(_pt1, _pt2, :ransac, 5)
+
+  dst_corners = []
+  4.times { |i|
+    x = src_corners[i].x
+    y = src_corners[i].y
+    z = 1.0 / (h[6][0] * x + h[7][0] * y + h[8][0])
+    x = (h[0][0] * x + h[1][0] * y + h[2][0]) * z
+    y = (h[3][0] * x + h[4][0] * y + h[5][0]) * z
+    dst_corners << CvPoint.new(x.to_i, y.to_i)
+  }
+
+  dst_corners
+end
+
+
+##### Main #####
+puts 'This program demonstrated the use of the SURF Detector and Descriptor using'
+puts 'brute force matching on planar objects.'
+puts 'Usage:'
+puts "ruby #{__FILE__} <object_filename> <scene_filename>, default is box.png and box_in_scene.png"
+puts
+
+object_filename = (ARGV.size == 2) ? ARGV[0] : 'box.png'
+scene_filename = (ARGV.size == 2) ? ARGV[1] : 'box_in_scene.png'
+
+object, image = nil, nil
+begin
+  object = IplImage.load(object_filename, CV_LOAD_IMAGE_GRAYSCALE)
+  image = IplImage.load(scene_filename, CV_LOAD_IMAGE_GRAYSCALE)
+rescue
+  puts "Can not load #{object_filename} and/or #{scene_filename}"
+  puts "Usage: ruby #{__FILE__} [<object_filename> <scene_filename>]"
+  exit
+end
+object_color = object.GRAY2BGR
+
+param = CvSURFParams.new(1500)
+
+object_keypoints, object_descriptors = nil, nil
+image_keypoints, image_descriptors = nil, nil
+tms = Benchmark.measure {
+  object_keypoints, object_descriptors = object.extract_surf(param)
+  puts "Object Descriptors: #{object_descriptors.size}"
+
+  image_keypoints, image_descriptors = image.extract_surf(param)
+  puts "Image Descriptors: #{image_descriptors.size}"
+}
+puts "Extraction time = #{tms.real * 1000} ms"
+
+correspond = IplImage.new(image.width, object.height + image.height, CV_8U, 1);
+correspond.set_roi(CvRect.new(0, 0, object.width, object.height))
+object.copy(correspond)
+correspond.set_roi(CvRect.new(0, object.height, image.width, image.height))
+image.copy(correspond)
+correspond.reset_roi
+
+src_corners = [CvPoint.new(0, 0), CvPoint.new(object.width, 0),
+               CvPoint.new(object.width, object.height), CvPoint.new(0, object.height)]
+dst_corners = locate_planar_object(object_keypoints, object_descriptors,
+                                   image_keypoints, image_descriptors, src_corners)
+
+correspond = correspond.GRAY2BGR
+if dst_corners
+  4.times { |i|
+    r1 = dst_corners[i % 4]
+    r2 = dst_corners[(i + 1) % 4]
+    correspond.line!(CvPoint.new(r1.x, r1.y + object.height), CvPoint.new(r2.x, r2.y + object.height),
+                     :color => CvColor::Red, :thickness => 2, :line_type => :aa)
+  }
+end
+
+ptpairs = find_pairs(object_keypoints, object_descriptors, image_keypoints, image_descriptors)
+
+0.step(ptpairs.size - 1, 2) { |i|
+  r1 = object_keypoints[ptpairs[i]]
+  r2 = image_keypoints[ptpairs[i + 1]]
+  correspond.line!(r1.pt, CvPoint.new(r2.pt.x, r2.pt.y + object.height),
+                   :color => CvColor::Red, :line_type => :aa)
+}
+
+object_keypoints.each { |r|
+  radius = (r.size * 1.2 / 9.0 * 2).to_i
+  object_color.circle!(r.pt, radius, :color => CvColor::Red, :line_type => :aa)
+}
+
+GUI::Window.new('Object Correspond').show correspond
+GUI::Window.new('Object').show object_color
+GUI::wait_key
+