1、arcLength函數

函數的作用

主要是計算圖像輪廓的周長、

2、函數調用形式

C++:?double?arcLength(InputArray?curve, bool?closed)

參數詳解：

InputArray?curve：表示圖像的輪廓

bool?closed：表示輪廓是否封閉的

3、一般圖像輪廓矩也可以算出圖像的周長和面積

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( argv[1], 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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