opencv学习笔记五十七：基于分水岭的图像分割

基本步骤：灰度二值化，形态学与距离变换再二值化，通过寻找轮廓与画轮廓生成种子点，分水岭分割，然后填色显示。

#include<opencv2\opencv.hpp>
using namespace cv;
using namespace std;

int main(int arc, char** argv) { 
	Mat src = imread("1.jpg");
	namedWindow("input", CV_WINDOW_AUTOSIZE);
	imshow("input", src);

	////灰度二值化
	Mat gray, binary;
	cvtColor(src, gray, CV_BGR2GRAY);
	threshold(gray, binary, 0, 255, THRESH_BINARY | THRESH_OTSU);
	imshow("binary", binary);

	//形态学与距离变换
	Mat kernel = getStructuringElement(MORPH_RECT, Size(3, 3));
	morphologyEx(binary, binary, MORPH_OPEN, kernel);
	Mat dist ;
	distanceTransform(binary, dist, 2, 3,CV_32F);//这里距离是选择L2，会有浮点数，所以类型为CV_32F
	normalize(dist, dist, 0, 1, NORM_MINMAX);
	imshow("distanceTransform", dist);
	threshold(dist, dist, 0.1, 1, THRESH_BINARY);
	normalize(dist, dist, 0, 255, NORM_MINMAX);
	dist.convertTo(dist, CV_8U);
	imshow("distanceTransform_binary", dist);

	//生成种子点
	vector<vector<Point>>contours;
	findContours(dist, contours, 3,CHAIN_APPROX_SIMPLE, Point(0, 0));
	Mat markers = Mat::zeros(src.size(), CV_32S);
	for (int i = 0; i < contours.size(); i++) {
		drawContours(markers, contours, i, Scalar(i+1), -1);//将Scalar值作为各类的索引值，则markers里的值为1到contours.size()
	}
	circle(markers, Point(5, 5), 3, Scalar(255), -1);//再加上个背景
	imshow("markers", markers*10000);


	//分水岭分割并显示
	watershed(src, markers);
	Mat mark;
	markers.convertTo(mark, CV_8UC1);
	//bitwise_not(mark, mark);
	imshow("watershed", mark*40);

	//用不同颜色显示
	Mat wshed(markers.size(), CV_8UC3);
	vector<Vec3b> colorTab;
	RNG rng(1);
	for (int i = 0; i <  contours.size(); i++)
	{
		int b = rng.uniform(0, 255);
		int g = rng.uniform(0, 255);
		int r = rng.uniform(0, 255);

		colorTab.push_back(Vec3b((uchar)b, (uchar)g, (uchar)r));
	}
	for (int i = 0; i < markers.rows; i++)
		for (int j = 0; j < markers.cols; j++)
		{
			int index = markers.at<int>(i, j);	
			if (index > 0 && index <= contours.size())
				wshed.at<Vec3b>(i, j) = colorTab[index - 1];
			else			
				wshed.at<Vec3b>(i, j) = Vec3b(0, 0, 0);
		}
	imshow("result", wshed);
	printf("number of objects:%d", contours.size());
	waitKey(0);
	return 0;
}