查找并绘制轮廓

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1.查找出轮廓，为了便于查找可以用canny边缘检测等等；
2.绘制轮廓；

#include <opencv2/opencv.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <opencv2/imgproc/imgproc.hpp>
using namespace cv;
using namespace std;

#define WINDOW_NAME1 "原始图窗口"
#define WINDOW_NAME2 "轮廓图"

Mat g_srcImage, g_grayImage;
int g_nThresh = 80, g_nThresh_max = 255;
RNG g_rng(12345);
Mat g_cannyMat_output;
vector<vector<Point>> g_vContours;
vector<Vec4i> g_vHierarchy;

void on_ThreshChange(int, void*)
{
	/*利用canny算子检测边缘*/
	Canny(g_grayImage, g_cannyMat_output, g_nThresh, g_nThresh * 2, 3);
	/*寻找轮廓*/
	findContours(g_cannyMat_output, g_vContours, g_vHierarchy, RETR_TREE, CHAIN_APPROX_SIMPLE, Point(0, 0));
	/*绘出轮廓*/
	Mat drawing = Mat::zeros(g_cannyMat_output.size(), CV_8UC3);
	for (int i = 0; i < g_vContours.size(); ++i)
	{
		Scalar color = Scalar(g_rng.uniform(0, 255), g_rng.uniform(0, 255), g_rng.uniform(0, 255));//任意值
		drawContours(drawing, g_vContours, i, color, 2, 8, g_vHierarchy, 0, Point());
	}
	imshow(WINDOW_NAME2, drawing);
}

int main()
{
	g_srcImage = imread("dlrb.jpg", 1);

	/*转化为灰度图并模糊化降噪*/
	cvtColor(g_srcImage, g_grayImage, COLOR_BGR2GRAY);
	blur(g_grayImage, g_grayImage, Size(3, 3));

	namedWindow(WINDOW_NAME1, WINDOW_AUTOSIZE);
	imshow(WINDOW_NAME1, g_srcImage);

	createTrackbar("canny阀值", WINDOW_NAME1, &g_nThresh, g_nThresh_max, on_ThreshChange);
	on_ThreshChange(0, 0);

	waitKey(0);
	return 0;
}

处理结果：