Add Java and Python code for the following imgproc tutorials: Finding contours in your image, Convex Hull, Creating Bounding boxes and circles for contours, Creating Bounding rotated boxes and ellipses for contours, Image Moments, Point Polygon Test.

samples/cpp/tutorial_code/ShapeDescriptors/moments_demo.cpp

@@ -8,13 +8,13 @@
 #include "opencv2/highgui.hpp"
 #include "opencv2/imgproc.hpp"
 #include <iostream>
+#include <iomanip>
 
 using namespace cv;
 using namespace std;
 
-Mat src; Mat src_gray;
+Mat src_gray;
 int thresh = 100;
-int max_thresh = 255;
 RNG rng(12345);
 
 /// Function header
@@ -25,31 +25,32 @@ void thresh_callback(int, void* );
  */
 int main( int argc, char** argv )
 {
-  /// Load source image and convert it to gray
-  CommandLineParser parser( argc, argv, "{@input | ../data/stuff.jpg | input image}" );
-  src = imread( parser.get<String>( "@input" ), IMREAD_COLOR );
+    /// Load source image
+    CommandLineParser parser( argc, argv, "{@input | ../data/stuff.jpg | input image}" );
+    Mat src = imread( parser.get<String>( "@input" ) );
 
-  if( src.empty() )
-  {
-      cout << "Could not open or find the image!\n" << endl;
-      cout << "usage: " << argv[0] << " <Input image>" << endl;
-      exit(0);
-  }
+    if( src.empty() )
+    {
+        cout << "Could not open or find the image!\n" << endl;
+        cout << "usage: " << argv[0] << " <Input image>" << endl;
+        return -1;
+    }
 
-  /// Convert image to gray and blur it
-  cvtColor( src, src_gray, COLOR_BGR2GRAY );
-  blur( src_gray, src_gray, Size(3,3) );
+    /// Convert image to gray and blur it
+    cvtColor( src, src_gray, COLOR_BGR2GRAY );
+    blur( src_gray, src_gray, Size(3,3) );
 
-  /// Create Window
-  const char* source_window = "Source";
-  namedWindow( source_window, WINDOW_AUTOSIZE );
-  imshow( source_window, src );
+    /// Create Window
+    const char* source_window = "Source";
+    namedWindow( source_window );
+    imshow( source_window, src );
 
-  createTrackbar( " Canny thresh:", "Source", &thresh, max_thresh, thresh_callback );
-  thresh_callback( 0, 0 );
+    const int max_thresh = 255;
+    createTrackbar( "Canny thresh:", source_window, &thresh, max_thresh, thresh_callback );
+    thresh_callback( 0, 0 );
 
-  waitKey(0);
-  return(0);
+    waitKey();
+    return 0;
 }
 
 /**
@@ -57,44 +58,47 @@ int main( int argc, char** argv )
  */
 void thresh_callback(int, void* )
 {
-  Mat canny_output;
-  vector<vector<Point> > contours;
+    /// Detect edges using canny
+    Mat canny_output;
+    Canny( src_gray, canny_output, thresh, thresh*2, 3 );
+    /// Find contours
+    vector<vector<Point> > contours;
+    findContours( canny_output, contours, RETR_TREE, CHAIN_APPROX_SIMPLE );
 
-  /// Detect edges using canny
-  Canny( src_gray, canny_output, thresh, thresh*2, 3 );
-  /// Find contours
-  findContours( canny_output, contours, RETR_TREE, CHAIN_APPROX_SIMPLE );
+    /// Get the moments
+    vector<Moments> mu(contours.size() );
+    for( size_t i = 0; i < contours.size(); i++ )
+    {
+        mu[i] = moments( contours[i] );
+    }
 
-  /// Get the moments
-  vector<Moments> mu(contours.size() );
-  for( size_t i = 0; i < contours.size(); i++ )
-     { mu[i] = moments( contours[i], false ); }
+    ///  Get the mass centers
+    vector<Point2f> mc( contours.size() );
+    for( size_t i = 0; i < contours.size(); i++ )
+    {
+        //add 1e-5 to avoid division by zero
+        mc[i] = Point2f( static_cast<float>(mu[i].m10 / (mu[i].m00 + 1e-5)),
+                         static_cast<float>(mu[i].m01 / (mu[i].m00 + 1e-5)) );
+        cout << "mc[" << i << "]=" << mc[i] << endl;
+    }
 
-  ///  Get the mass centers:
-  vector<Point2f> mc( contours.size() );
-  for( size_t i = 0; i < contours.size(); i++ )
-     { mc[i] = Point2f( static_cast<float>(mu[i].m10/mu[i].m00) , static_cast<float>(mu[i].m01/mu[i].m00) ); }
+    /// Draw contours
+    Mat drawing = Mat::zeros( canny_output.size(), CV_8UC3 );
+    for( size_t i = 0; i< contours.size(); i++ )
+    {
+        Scalar color = Scalar( rng.uniform(0, 256), rng.uniform(0,256), rng.uniform(0,256) );
+        drawContours( drawing, contours, (int)i, color, 2 );
+        circle( drawing, mc[i], 4, color, -1 );
+    }
 
-  /// Draw contours
-  Mat drawing = Mat::zeros( canny_output.size(), CV_8UC3 );
-  for( size_t i = 0; i< contours.size(); i++ )
-     {
-       Scalar color = Scalar( rng.uniform(0, 255), rng.uniform(0,255), rng.uniform(0,255) );
-       drawContours( drawing, contours, (int)i, color, 2, LINE_8 );
-       circle( drawing, mc[i], 4, color, -1, 8, 0 );
-     }
+    /// Show in a window
+    imshow( "Contours", drawing );
 
-  /// Show in a window
-  namedWindow( "Contours", WINDOW_AUTOSIZE );
-  imshow( "Contours", drawing );
-
-  /// Calculate the area with the moments 00 and compare with the result of the OpenCV function
-  printf("\t Info: Area and Contour Length \n");
-  for( size_t i = 0; i< contours.size(); i++ )
-     {
-       printf(" * Contour[%d] - Area (M_00) = %.2f - Area OpenCV: %.2f - Length: %.2f \n", (int)i, mu[i].m00, contourArea(contours[i]), arcLength( contours[i], true ) );
-       Scalar color = Scalar( rng.uniform(0, 255), rng.uniform(0,255), rng.uniform(0,255) );
-       drawContours( drawing, contours, (int)i, color, 2, LINE_8 );
-       circle( drawing, mc[i], 4, color, -1, 8, 0 );
-     }
+    /// Calculate the area with the moments 00 and compare with the result of the OpenCV function
+    cout << "\t Info: Area and Contour Length \n";
+    for( size_t i = 0; i < contours.size(); i++ )
+    {
+        cout << " * Contour[" << i << "] - Area (M_00) = " << std::fixed << std::setprecision(2) << mu[i].m00
+             << " - Area OpenCV: " << contourArea(contours[i]) << " - Length: " << arcLength( contours[i], true ) << endl;
+    }
 }