Cany算子检测图像轮廓

原理参考:

https://blog.csdn.net/tigerda/article/details/61192943

https://blog.csdn.net/jia20003/article/details/41173767

使用sobel算子实现：

edgedetector.h

#if !defined SOBELEDGES
#define SOBELEDGES

#define PI 3.1415926

#include <opencv2/core/core.hpp>
#include <opencv2/imgproc/imgproc.hpp>

class EdgeDetector {

private:

	// original image
	cv::Mat img;

	// 16-bit signed int image
	cv::Mat sobel;

	// Aperture size of the Sobel kernel
	int aperture;

	// Sobel magnitude
	cv::Mat sobelMagnitude;

	// Sobel orientation
	cv::Mat sobelOrientation;

public:

	EdgeDetector() : aperture(3) {}

	// Set the aperture size of the kernel
	void setAperture(int a) {

		aperture = a;
	}

	// Get the aperture size of the kernel
	int getAperture() const {

		return aperture;
	}

	// Compute the Sobel
	void computeSobel(const cv::Mat& image) {

		cv::Mat sobelX;
		cv::Mat sobelY;

		// Compute Sobel
		cv::Sobel(image, sobelX, CV_32F, 1, 0, aperture);
		cv::Sobel(image, sobelY, CV_32F, 0, 1, aperture);

		// Compute magnitude and orientation
		cv::cartToPolar(sobelX, sobelY, sobelMagnitude, sobelOrientation);
	}

	// Compute the Sobel
	void computeSobel(const cv::Mat& image, cv::Mat &sobelX, cv::Mat &sobelY) {

		// Compute Sobel
		cv::Sobel(image, sobelX, CV_32F, 1, 0, aperture);
		cv::Sobel(image, sobelY, CV_32F, 0, 1, aperture);

		// Compute magnitude and orientation
		cv::cartToPolar(sobelX, sobelY, sobelMagnitude, sobelOrientation);
	}

	// Get Sobel magnitude
	cv::Mat getMagnitude() {

		return sobelMagnitude;
	}

	// Get Sobel orientation
	cv::Mat getOrientation() {

		return sobelOrientation;
	}

	// Get a thresholded binary map
	cv::Mat getBinaryMap(double threshold) {

		cv::Mat bin;
		cv::threshold(sobelMagnitude, bin, threshold, 255, cv::THRESH_BINARY_INV);

		return bin;
	}

	// Get a CV_8U image of the Sobel
	cv::Mat getSobelImage() {

		cv::Mat bin;

		double minval, maxval;
		cv::minMaxLoc(sobelMagnitude, &minval, &maxval);
		sobelMagnitude.convertTo(bin, CV_8U, 255 / maxval);

		return bin;
	}

	// Get a CV_8U image of the Sobel orientation
	// 1 gray-level = 2 degrees
	cv::Mat getSobelOrientationImage() {

		cv::Mat bin;

		sobelOrientation.convertTo(bin, CV_8U, 90 / PI);

		return bin;
	}

};


#endif

#include <iostream>
#include <vector>
#include <opencv2/core.hpp>
#include <opencv2/imgproc.hpp>
#include <opencv2/highgui.hpp>
#include "edgedetector.h"

#define PI 3.1415926

int main()
{
	// Read input image
	cv::Mat image = cv::imread("E:\\OpenCV\\OpenCV3源码\\images\\road.jpg", 0);
	if (!image.data)
		return 0;

	// Display the image
	cv::namedWindow("Original Image");
	cv::imshow("Original Image", image);

	// Compute Sobel
	EdgeDetector ed;
	ed.computeSobel(image);

	// Display the Sobel orientation
	cv::namedWindow("Sobel (orientation)");
	cv::imshow("Sobel (orientation)", ed.getSobelOrientationImage());
	//cv::imwrite("ori.bmp", ed.getSobelOrientationImage());

	// Display the Sobel low threshold
	cv::namedWindow("Sobel (low threshold)");
	cv::imshow("Sobel (low threshold)", ed.getBinaryMap(125));

	// Display the Sobel high threshold
	cv::namedWindow("Sobel (high threshold)");
	cv::imshow("Sobel (high threshold)", ed.getBinaryMap(350));

结果：

 

使用canny算子：

// Apply Canny algorithm
	cv::Mat contours;
	cv::Canny(image, contours, 125, 350);

	// Display the image of contours
	cv::namedWindow("Canny Contours");
	cv::imshow("Canny Contours",255-contours);

结果：