approxPolyDP函数

1、approxPolyDP函数

函数的作用：

对图像轮廓点进行多边形拟合

2、函数的调用形式

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

参数详解;

InputArray curve:一般是由图像的轮廓点组成的点集

OutputArray approxCurve：表示输出的多边形点集

 double epsilon：主要表示输出的精度，就是另个轮廓点之间最大距离数，5,6,7，，8，，,,，

bool closed：表示输出的多边形是否封闭

3、opencv代码

#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 header
void thresh_callback(int, void*);

/** @function main */
int main(int argc, char** argv)
{
	/// 加载源图像
	src = imread("D:6.jpg", 1);

	/// 转成灰度图并进行模糊降噪
	cvtColor(src, src_gray, CV_BGR2GRAY);
	blur(src_gray, src_gray, Size(3, 3));

	/// 创建窗体
	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 src_copy = src.clone();
	Mat threshold_output;
	vector<vector<Point> > contours;
	vector<Vec4i> hierarchy;

	/// 对图像进行二值化
	threshold(src_gray, threshold_output, thresh, 255, THRESH_BINARY);

	/// 寻找轮廓
	findContours(threshold_output, contours, hierarchy, CV_RETR_TREE, CV_CHAIN_APPROX_SIMPLE, Point(0, 0));
	/*Mat drawing = Mat::zeros(threshold_output.size(), CV_8UC3);*/

	/* 对每个轮廓计算其凸包*/
	vector<vector<Point> >poly(contours.size());
	for (int i = 0; i < contours.size(); i++)
	{
		approxPolyDP(Mat(contours[i]), poly[i], 5,true);
	}

	/* 绘出轮廓及其凸包*/
	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, i, color, 1, 8, vector<Vec4i>(), 0, Point());
		drawContours(drawing, poly, i, color, 1, 8, vector<Vec4i>(), 0, Point());
	}
	/*vector<Point> poly;
	approxPolyDP(Mat(contours[3]), poly, 5, false);
	vector<Point>::const_iterator itp = poly.begin();
	while (itp != (poly.end() - 2))
	{
		line(drawing, *itp, *(itp + 1), Scalar(255), 2);
		++itp;
	}
	line(drawing, *itp, *(poly.begin()), Scalar(255), 2);*/
	/// 把结果显示在窗体
	namedWindow("Hull demo", CV_WINDOW_AUTOSIZE);
	imshow("Hull demo", drawing);
}