OpenCV 計算物體的凸包

• 使用OpenCV函數 convexHull

步驟

1. 濾波——消除噪聲
2. 增強——二值化，使輪廓更明顯
3. 檢測——選出邊緣點
4. 計算凸包

例程

#include "opencv2/highgui/highgui.hpp"
#include "opencv2/imgproc/imgproc.hpp"
#include <opencv2/highgui/highgui_c.h>
#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)
{
	/// 加載源圖像
	src = imread("../images/hands2.jpg");

	/// 轉成灰度圖並進行模糊降噪
	cvtColor(src, src_gray, CV_BGR2GRAY);
	blur(src_gray, src_gray, Size(3, 3));

	/// 創建窗體
	const 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;

	/// 對圖像進行二值化
	threshold(src_gray, threshold_output, thresh, 255, THRESH_BINARY);

	/// 尋找輪廓
	findContours(threshold_output, contours, hierarchy, CV_RETR_TREE, CV_CHAIN_APPROX_SIMPLE, Point(0, 0));

	/// 對每個輪廓計算其凸包
	vector<vector<Point> >hull(contours.size());
	for (int i = 0; i < contours.size(); i++)
	{
		convexHull(Mat(contours[i]), hull[i], false);
	}

	/// 繪出輪廓及其凸包
	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, hull, i, color, 1, 8, vector<Vec4i>(), 0, Point());
	}

	/// 把結果顯示在窗體
	namedWindow("Hull demo", CV_WINDOW_AUTOSIZE);
	imshow("Hull demo", drawing);
}