1、contourArea函數

函數作用

主要用于計算圖像輪廓的面積

2、contourArea函數調用形式

C++:?double?contourArea(InputArray?contour, bool?oriented=false?)

參數詳解：

InputArray?contour：輸入的點，一般是圖像的輪廓點

bool?oriented=false:表示某一個方向上輪廓的的面積值，順時針或者逆時針，一般選擇默認false

3、opencv代碼：

#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);/// 函數聲明 void thresh_callback(int, void*);/** @主函數 */ int main(int argc, char** argv) {/// 讀入原圖像, 返回3通道圖像數據src = imread("D:6.jpg", 1);/// 把原圖像轉化成灰度圖像并進行平滑cvtColor(src, src_gray, CV_BGR2GRAY);blur(src_gray, src_gray, Size(3, 3));/// 創建新窗口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 函數 */ void thresh_callback(int, void*) {Mat canny_output;vector<vector<Point> > contours;vector<Vec4i> hierarchy;/// 使用Canndy檢測邊緣Canny(src_gray, canny_output, thresh, thresh * 2, 3);/// 找到輪廓findContours(canny_output, contours, hierarchy, CV_RETR_TREE, CV_CHAIN_APPROX_SIMPLE, Point(0, 0));/// 計算矩vector<Moments> mu(contours.size());for (int i = 0; i < contours.size(); i++){mu[i] = moments(contours[i], false);}/// 計算中心矩: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);}/// 繪制輪廓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);}/// 顯示到窗口中namedWindow("Contours", CV_WINDOW_AUTOSIZE);imshow("Contours", drawing);/// 通過m00計算輪廓面積并且和OpenCV函數比較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);} }

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