外接旋转矩形 ，或外接椭圆

RotatedRect minAreaRect(InputArray points)

返回面积最小的外接矩形

RotatedRect fitEllipse(InputArray points)

The function calculates the ellipse that fits (in a least-squares sense) a set of 2D points best of all. It returns the rotated rectangle in which the ellipse is inscribed.

Code

#include "stdafx.h"#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);/// Function headervoid thresh_callback(int, void* );/** @function main */int main( int argc, char** argv ){	/// Load source image and convert it to gray	src = http://www.mamicode.com/imread("img2.jpg", 1 );	/// Convert image to gray and blur it	cvtColor( src, src_gray, CV_BGR2GRAY );	blur( src_gray, src_gray, Size(3,3) );	/// Create Window	char* source_window = "Source";	namedWindow( source_window, CV_WINDOW_AUTOSIZE );	imshow( source_window, src );	createTrackbar( " Threshold:", "Source", &thresh, max_thresh, thresh_callback );	thresh_callback( 0, 0 );	waitKey(0);	return(0);}/** @function thresh_callback */void thresh_callback(int, void* ){	Mat threshold_output;	vector<vector<Point> > contours;	vector<Vec4i> hierarchy;	/// Detect edges using Threshold	threshold( src_gray, threshold_output, thresh, 255, THRESH_BINARY );	/// Find contours	findContours( threshold_output, contours, hierarchy, CV_RETR_TREE, CV_CHAIN_APPROX_SIMPLE, Point(0, 0) );	/// Find the rotated rectangles and ellipses for each contour	vector<RotatedRect> minRect( contours.size() );	vector<RotatedRect> minEllipse( contours.size() );	for( int i = 0; i < contours.size(); i++ )	{ 		minRect[i] = minAreaRect( Mat(contours[i]) );		if( contours[i].size() > 5 )			{ minEllipse[i] = fitEllipse( Mat(contours[i]) ); }	}	/// Draw contours + rotated rects + ellipses	Mat drawing = Mat::zeros( threshold_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) );		// contour		drawContours( drawing, contours, i, color, 1, 8, vector<Vec4i>(), 0, Point() );		// ellipse		ellipse( drawing, minEllipse[i], color, 2, 8 );		// rotated rectangle		Point2f rect_points[4]; minRect[i].points( rect_points );		for( int j = 0; j < 4; j++ )			line( drawing, rect_points[j], rect_points[(j+1)%4], color, 1, 8 );	}	/// Show in a window	namedWindow( "Contours", CV_WINDOW_AUTOSIZE );	imshow( "Contours", drawing );}

OpenCV Tutorials —— Creating Bounding rotated boxes and ellipses for contours