init - 初始化项目

samples/cpp/tutorial_code/ShapeDescriptors/moments_demo.cpp

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+/**
+ * @function moments_demo.cpp
+ * @brief Demo code to calculate moments
+ * @author OpenCV team
+ */
+
+#include "opencv2/imgcodecs.hpp"
+#include "opencv2/highgui.hpp"
+#include "opencv2/imgproc.hpp"
+#include <iostream>
+#include <iomanip>
+
+using namespace cv;
+using namespace std;
+
+Mat src_gray;
+int thresh = 100;
+RNG rng(12345);
+
+/// Function header
+void thresh_callback(int, void* );
+
+/**
+ * @function main
+ */
+int main( int argc, char** argv )
+{
+    /// Load source image
+    CommandLineParser parser( argc, argv, "{@input | stuff.jpg | input image}" );
+    Mat src = imread( samples::findFile( parser.get<String>( "@input" ) ) );
+
+    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) );
+
+    /// Create Window
+    const char* source_window = "Source";
+    namedWindow( source_window );
+    imshow( source_window, src );
+
+    const int max_thresh = 255;
+    createTrackbar( "Canny thresh:", source_window, &thresh, max_thresh, thresh_callback );
+    thresh_callback( 0, 0 );
+
+    waitKey();
+    return 0;
+}
+
+/**
+ * @function thresh_callback
+ */
+void thresh_callback(int, void* )
+{
+    /// 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 );
+
+    /// Get the moments
+    vector<Moments> mu(contours.size() );
+    for( size_t i = 0; i < contours.size(); i++ )
+    {
+        mu[i] = moments( contours[i] );
+    }
+
+    ///  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;
+    }
+
+    /// 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 );
+    }
+
+    /// Show in a window
+    imshow( "Contours", drawing );
+
+    /// 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;
+    }
+}