opencv/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 s_ranges[] = { 0, 256 };
    float h_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;
}