approxPolyDP-轮廓近似

approxPolyDP-轮廓近似

参考：http://blog.csdn.net/qq_18343569/article/details/47999257

approxPolyDP函数

python版轮廓近似

http://blog.csdn.net/zhangxb35/article/details/47275277

code源码：https://github.com/Itseez/opencv/tree/master/samples/cpp/contours2.cpp

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

[cpp] view
plain copy

#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);

}