Added generalContours_demo1.cpp tutorial code

samples/cpp/tutorial_code/ShapeDescriptors/generalContours_demo1.cpp

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+/**
+ * @function generalContours_demo1.cpp
+ * @brief Demo code to find contours in an image
+ * @author OpenCV team
+ */
+
+#include "opencv2/highgui/highgui.hpp"
+#include "opencv2/imgproc/imgproc.hpp"
+#include <iostream>
+#include <stdio.h>
+#include <stdlib.h>
+
+using namespace cv;
+using namespace std;
+
+Mat src; Mat src_gray;
+int thresh = 100;
+int max_thresh = 255;
+RNG rng(12345);
+
+/// Function header
+void thresh_callback(int, void* );
+
+/**
+ * @function main
+ */
+int main( int argc, char** argv )
+{
+  /// Load source image and convert it to gray
+  src = imread( argv[1], 1 );
+
+  /// Convert image to gray and blur it
+  cvtColor( src, src_gray, CV_BGR2GRAY );
+  blur( src_gray, src_gray, Size(3,3) );
+
+  /// Create Window
+  char* source_window = "Source";
+  namedWindow( source_window, CV_WINDOW_AUTOSIZE );
+  imshow( source_window, src );
+
+  createTrackbar( " Threshold:", "Source", &thresh, max_thresh, thresh_callback );
+  thresh_callback( 0, 0 );
+
+  waitKey(0);
+  return(0);
+}
+
+/**
+ * @function thresh_callback
+ */
+void thresh_callback(int, void* )
+{
+  Mat threshold_output;
+  vector<vector<Point> > contours;
+  vector<Vec4i> hierarchy;
+
+  /// Detect edges using Threshold
+  threshold( src_gray, threshold_output, thresh, 255, THRESH_BINARY );
+  /// Find contours  
+  findContours( threshold_output, contours, hierarchy, CV_RETR_TREE, CV_CHAIN_APPROX_SIMPLE, Point(0, 0) );
+
+  /// Approximate contours to polygons + get bounding rects and circles
+  vector<vector<Point> > contours_poly( contours.size() );
+  vector<Rect> boundRect( contours.size() );
+  vector<Point2f>center( contours.size() );
+  vector<float>radius( contours.size() );
+
+  for( int i = 0; i < contours.size(); i++ )
+     { approxPolyDP( Mat(contours[i]), contours_poly[i], 3, true ); 
+       boundRect[i] = boundingRect( Mat(contours_poly[i]) ); 
+       minEnclosingCircle( contours_poly[i], center[i], radius[i] );
+     } 
+
+
+  /// Draw polygonal contour + bonding rects + circles
+  Mat drawing = Mat::zeros( threshold_output.size(), CV_8UC3 );
+  for( int i = 0; i< contours.size(); i++ )
+     { 
+       Scalar color = Scalar( rng.uniform(0, 255), rng.uniform(0,255), rng.uniform(0,255) );
+       drawContours( drawing, contours_poly, i, color, 1, 8, vector<Vec4i>(), 0, Point() ); 
+       rectangle( drawing, boundRect[i].tl(), boundRect[i].br(), color, 2, 8, 0 );
+       circle( drawing, center[i], (int)radius[i], color, 2, 8, 0 );
+     }
+
+  /// Show in a window
+  namedWindow( "Contours", CV_WINDOW_AUTOSIZE );
+  imshow( "Contours", drawing );
+}