/**
 * @file BackProject_Demo1.cpp
 * @brief Sample code for backproject function usage
 * @author OpenCV team
 */

#include "opencv2/imgproc.hpp"
#include "opencv2/imgcodecs.hpp"
#include "opencv2/highgui.hpp"

#include <iostream>

using namespace cv;
using namespace std;

/// Global Variables
Mat src; Mat hsv; Mat hue;
int bins = 25;

/// Function Headers
void Hist_and_Backproj(int, void* );


/**
 * @function main
 */
int main( int, char** argv )
{
  /// Read the image
  src = imread( argv[1], IMREAD_COLOR );

  if( src.empty() )
    { cout<<"Usage: ./calcBackProject_Demo1 <path_to_image>"<<endl;
      return -1;
    }

  /// Transform it to HSV
  cvtColor( src, hsv, COLOR_BGR2HSV );

  /// Use only the Hue value
  hue.create( hsv.size(), hsv.depth() );
  int ch[] = { 0, 0 };
  mixChannels( &hsv, 1, &hue, 1, ch, 1 );

  /// Create Trackbar to enter the number of bins
  const char* window_image = "Source image";
  namedWindow( window_image, WINDOW_AUTOSIZE );
  createTrackbar("* Hue  bins: ", window_image, &bins, 180, Hist_and_Backproj );
  Hist_and_Backproj(0, 0);

  /// Show the image
  imshow( window_image, src );

  /// Wait until user exits the program
  waitKey(0);
  return 0;
}


/**
 * @function Hist_and_Backproj
 * @brief Callback to Trackbar
 */
void Hist_and_Backproj(int, void* )
{
  MatND hist;
  int histSize = MAX( bins, 2 );
  float hue_range[] = { 0, 180 };
  const float* ranges = { hue_range };

  /// Get the Histogram and normalize it
  calcHist( &hue, 1, 0, Mat(), hist, 1, &histSize, &ranges, true, false );
  normalize( hist, hist, 0, 255, NORM_MINMAX, -1, Mat() );

  /// Get Backprojection
  MatND backproj;
  calcBackProject( &hue, 1, 0, hist, backproj, &ranges, 1, true );

  /// Draw the backproj
  imshow( "BackProj", backproj );

  /// Draw the histogram
  int w = 400; int h = 400;
  int bin_w = cvRound( (double) w / histSize );
  Mat histImg = Mat::zeros( w, h, CV_8UC3 );

  for( int i = 0; i < bins; i ++ )
     { rectangle( histImg, Point( i*bin_w, h ), Point( (i+1)*bin_w, h - cvRound( hist.at<float>(i)*h/255.0 ) ), Scalar( 0, 0, 255 ), -1 ); }

  imshow( "Histogram", histImg );

}
