同样是提取出轮廓之后的处理 ~~

void approxPolyDP(InputArray curve, OutputArray approxCurve, double epsilon, bool closed)

Parameters:

• curve –

  Input vector of a 2D point stored in:

  • std::vector or Mat (C++ interface)
  • Nx2 numpy array (Python interface)
  • CvSeq or CvMat (C interface)
• approxCurve – Result of the approximation. The type should match the type of the input curve. In case of C interface the approximated curve is stored in the memory storage and pointer to it is returned.
• epsilon – Parameter specifying the approximation accuracy. This is the maximum distance between the original curve and its approximation.
• closed – If true, the approximated curve is closed (its first and last vertices are connected). Otherwise, it is not closed.
• header_size – Header size of the approximated curve. Normally, sizeof(CvContour) is used.
• storage – Memory storage where the approximated curve is stored.
• method – Contour approximation algorithm. Only CV_POLY_APPROX_DP is supported.
• recursive – Recursion flag. If it is non-zero and curve is CvSeq*, the function cvApproxPolyapproximates all the contours accessible from curve by h_next and v_next links.

Rect boundingRect(InputArray points)

Calculates the up-right bounding rectangle of a point set.

void minEnclosingCircle(InputArray points, Point2f& center, float& radius)

Parameters:

• points –

  Input vector of 2D points, stored in:

  • std::vector<> or Mat (C++ interface)
  • CvSeq* or CvMat* (C interface)
  • Nx2 numpy array (Python interface)
• center – Output center of the circle.
• radius – Output radius of the circle.

 

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) );	// 均值滤波 —— 去除小的噪声	/// 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) );	/// Approximate contours to polygons + get bounding rects and circles	vector<vector<Point> > contours_poly( contours.size() );	vector<Rect> boundRect( contours.size() );	vector<Point2f>center( contours.size() );	vector<float>radius( contours.size() );	for( int i = 0; i < contours.size(); i++ )	{ 		approxPolyDP( Mat(contours[i]), contours_poly[i], 3, true );	// 原始曲线和近似曲线的精度为3， 近似曲线封闭		boundRect[i] = boundingRect( Mat(contours_poly[i]) );		minEnclosingCircle( (Mat)contours_poly[i], center[i], radius[i] );	}	/// Draw polygonal contour + bonding rects + circles	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) );		drawContours( drawing, contours_poly, i, color, 1, 8, vector<Vec4i>(), 0, Point() );		rectangle( drawing, boundRect[i].tl(), boundRect[i].br(), color, 2, 8, 0 );		circle( drawing, center[i], (int)radius[i], color, 2, 8, 0 );	}	/// Show in a window	namedWindow( "Contours", CV_WINDOW_AUTOSIZE );	imshow( "Contours", drawing );}

OpenCV Tutorials —— Creating Bounding boxes and circles for contours