opencv c++函数 imgproc模块 23 轮廓矩

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目标

在这节教程中您将学到:

  • 使用OpenCV函数 moments 计算图像所有的矩(最高到3阶)
  • 使用OpenCV函数 contourArea 来计算轮廓面积
  • 使用OpenCV函数 arcLength 来计算轮廓或曲线长度

原理

代码

下面是本节教程源码. 你也可以从 这里 下载.

#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);/// 函数声明void thresh_callback(int, void* );/** @主函数 */int main( int argc, char** argv ){  /// 读入原图像, 返回3通道图像数据  src = imread( argv[1], 1 );  /// 把原图像转化成灰度图像并进行平滑  cvtColor( src, src_gray, CV_BGR2GRAY );  blur( src_gray, src_gray, Size(3,3) );  /// 创建新窗口  char* source_window = "Source";  namedWindow( source_window, CV_WINDOW_AUTOSIZE );  imshow( source_window, src );  createTrackbar( " Canny thresh:", "Source", &thresh, max_thresh, thresh_callback );  thresh_callback( 0, 0 );  waitKey(0);  return(0);}/** @thresh_callback 函数 */void thresh_callback(int, void* ){  Mat canny_output;  vector<vector<Point> > contours;  vector<Vec4i> hierarchy;  /// 使用Canndy检测边缘  Canny( src_gray, canny_output, thresh, thresh*2, 3 );  /// 找到轮廓  findContours( canny_output, contours, hierarchy, CV_RETR_TREE, CV_CHAIN_APPROX_SIMPLE, Point(0, 0) );  /// 计算矩  vector<Moments> mu(contours.size() );  for( int i = 0; i < contours.size(); i++ )     { mu[i] = moments( contours[i], false ); }  ///  计算中心矩:  vector<Point2f> mc( contours.size() );  for( int i = 0; i < contours.size(); i++ )     { mc[i] = Point2f( mu[i].m10/mu[i].m00 , mu[i].m01/mu[i].m00 ); }  /// 绘制轮廓  Mat drawing = Mat::zeros( canny_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, i, color, 2, 8, hierarchy, 0, Point() );       circle( drawing, mc[i], 4, color, -1, 8, 0 );     }  /// 显示到窗口中  namedWindow( "Contours", CV_WINDOW_AUTOSIZE );  imshow( "Contours", drawing );  /// 通过m00计算轮廓面积并且和OpenCV函数比较  printf("\t Info: Area and Contour Length \n");  for( int i = 0; i< contours.size(); i++ )     {       printf(" * Contour[%d] - Area (M_00) = %.2f - Area OpenCV: %.2f - Length: %.2f \n", 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, i, color, 2, 8, hierarchy, 0, Point() );       circle( drawing, mc[i], 4, color, -1, 8, 0 );     }}

代码说明

结果

  1. 如下所示:

    MU_0

    MU_1

    MU_2

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