Added calcBackProject_Demo1.cpp for tutorial sample code

samples/cpp/tutorial_code/Histograms_Matching/calcBackProject_Demo1.cpp

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+/**
+ * @file BackProject_Demo1.cpp
+ * @brief Sample code for backproject function usage
+ * @author OpenCV team
+ */
+
+#include "opencv2/imgproc/imgproc.hpp"
+#include "opencv2/highgui/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 argc, char** argv )
+{
+  /// Read the image
+  src = imread( argv[1], 1 );
+  /// Transform it to HSV
+  cvtColor( src, hsv, CV_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
+  char* window_image = "Source image";
+  namedWindow( window_image, CV_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 );
+
+}