Added compareHist_demo.cpp code

samples/cpp/tutorial_code/Histograms_Matching/compareHist_Demo.cpp

+/**
+ * @file compareHist_Demo.cpp
+ * @brief Sample code to use the function compareHist
+ * @author OpenCV team
+ */
+
+#include "opencv2/highgui/highgui.hpp"
+#include "opencv2/imgproc/imgproc.hpp"
+#include <iostream>
+#include <stdio.h>
+
+using namespace std;
+using namespace cv;
+
+/**
+ * @function main
+ */
+int main( int argc, char** argv )
+{
+    Mat src_base, hsv_base;
+    Mat src_test1, hsv_test1;
+    Mat src_test2, hsv_test2;
+    Mat hsv_half_down;
+
+   /// Load three images with different environment settings
+   if( argc < 4 )
+     { printf("** Error. Usage: ./compareHist_Demo <image_settings0> <image_setting1> <image_settings2>\n");
+       return -1; 
+     }
+
+   src_base = imread( argv[1], 1 );
+   src_test1 = imread( argv[2], 1 );
+   src_test2 = imread( argv[3], 1 );
+
+   /// Convert to HSV
+   cvtColor( src_base, hsv_base, CV_BGR2HSV );
+   cvtColor( src_test1, hsv_test1, CV_BGR2HSV );
+   cvtColor( src_test2, hsv_test2, CV_BGR2HSV );
+
+   hsv_half_down = hsv_base( Range( hsv_base.rows/2, hsv_base.rows - 1 ), Range( 0, hsv_base.cols - 1 ) );  
+
+   /// Using 30 bins for hue and 32 for saturation
+    int h_bins = 50; int s_bins = 60;
+    int histSize[] = { h_bins, s_bins };
+
+    // hue varies from 0 to 256, saturation from 0 to 180
+    float h_ranges[] = { 0, 256 };
+    float s_ranges[] = { 0, 180 };
+
+    const float* ranges[] = { h_ranges, s_ranges };
+
+    // Use the o-th and 1-st channels
+    int channels[] = { 0, 1 };
+
+
+    /// Histograms
+    MatND hist_base;
+    MatND hist_half_down;
+    MatND hist_test1;
+    MatND hist_test2;
+
+    /// Calculate the histograms for the HSV images
+    calcHist( &hsv_base, 1, channels, Mat(), hist_base, 2, histSize, ranges, true, false );
+    normalize( hist_base, hist_base, 0, 1, NORM_MINMAX, -1, Mat() );
+
+    calcHist( &hsv_half_down, 1, channels, Mat(), hist_half_down, 2, histSize, ranges, true, false );
+    normalize( hist_half_down, hist_half_down, 0, 1, NORM_MINMAX, -1, Mat() );
+
+    calcHist( &hsv_test1, 1, channels, Mat(), hist_test1, 2, histSize, ranges, true, false );
+    normalize( hist_test1, hist_test1, 0, 1, NORM_MINMAX, -1, Mat() );
+
+    calcHist( &hsv_test2, 1, channels, Mat(), hist_test2, 2, histSize, ranges, true, false );
+    normalize( hist_test2, hist_test2, 0, 1, NORM_MINMAX, -1, Mat() );
+
+    /// Apply the histogram comparison methods
+    for( int i = 0; i < 4; i++ )
+       { int compare_method = i; 
+         double base_base = compareHist( hist_base, hist_base, compare_method );
+         double base_half = compareHist( hist_base, hist_half_down, compare_method );
+         double base_test1 = compareHist( hist_base, hist_test1, compare_method );
+         double base_test2 = compareHist( hist_base, hist_test2, compare_method );
+     
+         printf( " Method [%d] Perfect, Base-Half, Base-Test(1), Base-Test(2) : %f, %f, %f, %f \n", i, base_base, base_half , base_test1, base_test2 );
+       } 
+
+    printf( "Done \n" );
+
+    return 0;
+}