初步图像分析

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一、使用傅里叶变换进行卷积

代码示例

#include 
#include 

using namespace std;

static void test() {
	string path = "lena.jpg";
	cv::Mat A = cv::imread(path, 0);
	if (A.empty()) {
		cout << "can not load image" << endl;
		return ;
	}

	cv::Size patchSize(100, 100);
	cv::Point topleft(A.cols / 2, A.rows / 2);
	cv::Rect roi(topleft.x, topleft.y, patchSize.width, patchSize.height);
	cv::Mat B = A(roi);

	int dft_M = cv::getOptimalDFTSize(A.rows + B.rows - 1);
	int dft_N = cv::getOptimalDFTSize(A.cols + B.cols - 1);

	cv::Mat dft_A = cv::Mat::zeros(dft_M, dft_N, CV_32F);
	cv::Mat dft_B = cv::Mat::zeros(dft_M, dft_N, CV_32F);

	cv::Mat dft_A_part = dft_A(cv::Rect(0, 0, A.cols, A.rows));
	cv::Mat dft_B_part = dft_B(cv::Rect(0, 0, B.cols, B.rows));

	A.convertTo(dft_A_part, dft_A_part.type(), 1, -mean(A)[0]);
	B.convertTo(dft_B_part, dft_B_part.type(), 1, -mean(B)[0]);

	cv::dft(dft_A, dft_A, 0, A.rows);
	cv::dft(dft_B, dft_B, 0, B.rows);

	// set the last parameter to false to compute convolution instead of correlation
	//
	cv::mulSpectrums(dft_A, dft_B, dft_A, 0, true);
	cv::idft(dft_A, dft_A, cv::DFT_SCALE, A.rows + B.rows - 1);

	cv::Mat corr = dft_A(cv::Rect(0, 0, A.cols + B.cols - 1, A.rows + B.rows - 1));
	cv::normalize(corr, corr, 0, 1, cv::NORM_MINMAX, corr.type());
	cv::pow(corr, 3.0, corr);

	B ^= cv::Scalar::all(255);

	cv::imshow("Image", A);
	cv::imshow("ROI", B);

	cv::imshow("Correlation", corr);
	cv::waitKey();
}


int main()
{
	test();
	system("pause");
	return 0;
}

结果

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二、用HoughCircles()从灰度图中获取一组圆的序列

代码示例

#include 
#include 

using namespace std;

static void test() {
	cv::Mat src, image;
	string path = "Image.jpg";

	src = cv::imread(path);
	if (src.empty()) {
		cout << "Cannot load image" << endl;
		return ;
	}

	cv::cvtColor(src, image, cv::COLOR_BGR2GRAY);
	cv::GaussianBlur(image, image, cv::Size(5, 5), 0, 0);

	vector<cv::Vec3f> circles;
	cv::HoughCircles(image, circles, cv::HOUGH_GRADIENT, 2, image.cols / 4);

	for (size_t i = 0; i < circles.size(); ++i) {
		cv::circle(src,
			cv::Point(cvRound(circles[i][0]), cvRound(circles[i][1])),
			cvRound(circles[i][2]),
			cv::Scalar(0, 0, 255),
			2,
			cv::LINE_AA);
	}

	cv::imshow("Hough Circles", src);
	cv::waitKey(0);
}

int main()
{
	test();
	system("pause");
	return 0;
}

结果

三、分割

代码

#include "opencv2/imgcodecs.hpp"
#include "opencv2/highgui.hpp"
#include "opencv2/imgproc.hpp"

#include 

using namespace std;
using namespace cv;

static void help(char** argv)
{
	cout << "\nThis program demonstrates GrabCut segmentation -- select an object in a region\n"
		"and then grabcut will attempt to segment it out.\n"
		"Call:\n"
		<< argv[0] << " \n"
		"\nSelect a rectangular area around the object you want to segment\n" <<
		"\nHot keys: \n"
		"\tESC - quit the program\n"
		"\tr - restore the original image\n"
		"\tn - next iteration\n"
		"\n"
		"\tleft mouse button - set rectangle\n"
		"\n"
		"\tCTRL+left mouse button - set GC_BGD pixels\n"
		"\tSHIFT+left mouse button - set GC_FGD pixels\n"
		"\n"
		"\tCTRL+right mouse button - set GC_PR_BGD pixels\n"
		"\tSHIFT+right mouse button - set GC_PR_FGD pixels\n" << endl;
}

const Scalar RED = Scalar(0, 0, 255);
const Scalar PINK = Scalar(230, 130, 255);
const Scalar BLUE = Scalar(255, 0, 0);
const Scalar LIGHTBLUE = Scalar(255, 255, 160);
const Scalar GREEN = Scalar(0, 255, 0);

const int BGD_KEY = EVENT_FLAG_CTRLKEY;
const int FGD_KEY = EVENT_FLAG_SHIFTKEY;

static void getBinMask(const Mat& comMask, Mat& binMask)
{
	if (comMask.empty() || comMask.type() != CV_8UC1)
		CV_Error(Error::StsBadArg, "comMask is empty or has incorrect type (not CV_8UC1)");
	if (binMask.empty() || binMask.rows != comMask.rows || binMask.cols != comMask.cols)
		binMask.create(comMask.size(), CV_8UC1);
	binMask = comMask & 1;
}

class GCApplication
{
public:
	enum { NOT_SET = 0, IN_PROCESS = 1, SET = 2 };
	static const int radius = 2;
	static const int thickness = -1;

	void reset();
	void setImageAndWinName(const Mat& _image, const string& _winName);
	void showImage() const;
	void mouseClick(int event, int x, int y, int flags, void* param);
	int nextIter();
	int getIterCount() const { return iterCount; }
private:
	void setRectInMask();
	void setLblsInMask(int flags, Point p, bool isPr);

	const string* winName;
	const Mat* image;
	Mat mask;
	Mat bgdModel, fgdModel;

	uchar rectState, lblsState, prLblsState;
	bool isInitialized;

	Rect rect;
	vector<Point> fgdPxls, bgdPxls, prFgdPxls, prBgdPxls;
	int iterCount;
};

void GCApplication::reset()
{
	if (!mask.empty())
		mask.setTo(Scalar::all(GC_BGD));
	bgdPxls.clear(); fgdPxls.clear();
	prBgdPxls.clear();  prFgdPxls.clear();

	isInitialized = false;
	rectState = NOT_SET;
	lblsState = NOT_SET;
	prLblsState = NOT_SET;
	iterCount = 0;
}

void GCApplication::setImageAndWinName(const Mat& _image, const string& _winName)
{
	if (_image.empty() || _winName.empty())
		return;
	image = &_image;
	winName = &_winName;
	mask.create(image->size(), CV_8UC1);
	reset();
}

void GCApplication::showImage() const
{
	if (image->empty() || winName->empty())
		return;

	Mat res;
	Mat binMask;
	if (!isInitialized)
		image->copyTo(res);
	else
	{
		getBinMask(mask, binMask);
		image->copyTo(res, binMask);
	}

	vector<Point>::const_iterator it;
	for (it = bgdPxls.begin(); it != bgdPxls.end(); ++it)
		circle(res, *it, radius, BLUE, thickness);
	for (it = fgdPxls.begin(); it != fgdPxls.end(); ++it)
		circle(res, *it, radius, RED, thickness);
	for (it = prBgdPxls.begin(); it != prBgdPxls.end(); ++it)
		circle(res, *it, radius, LIGHTBLUE, thickness);
	for (it = prFgdPxls.begin(); it != prFgdPxls.end(); ++it)
		circle(res, *it, radius, PINK, thickness);

	if (rectState == IN_PROCESS || rectState == SET)
		rectangle(res, Point(rect.x, rect.y), Point(rect.x + rect.width, rect.y + rect.height), GREEN, 2);

	imshow(*winName, res);
}

void GCApplication::setRectInMask()
{
	CV_Assert(!mask.empty());
	mask.setTo(GC_BGD);
	rect.x = max(0, rect.x);
	rect.y = max(0, rect.y);
	rect.width = min(rect.width, image->cols - rect.x);
	rect.height = min(rect.height, image->rows - rect.y);
	(mask(rect)).setTo(Scalar(GC_PR_FGD));
}

void GCApplication::setLblsInMask(int flags, Point p, bool isPr)
{
	vector<Point> *bpxls, *fpxls;
	uchar bvalue, fvalue;
	if (!isPr)
	{
		bpxls = &bgdPxls;
		fpxls = &fgdPxls;
		bvalue = GC_BGD;
		fvalue = GC_FGD;
	}
	else
	{
		bpxls = &prBgdPxls;
		fpxls = &prFgdPxls;
		bvalue = GC_PR_BGD;
		fvalue = GC_PR_FGD;
	}
	if (flags & BGD_KEY)
	{
		bpxls->push_back(p);
		circle(mask, p, radius, bvalue, thickness);
	}
	if (flags & FGD_KEY)
	{
		fpxls->push_back(p);
		circle(mask, p, radius, fvalue, thickness);
	}
}

void GCApplication::mouseClick(int event, int x, int y, int flags, void*)
{
	// TODO add bad args check
	switch (event)
	{
	case EVENT_LBUTTONDOWN: // set rect or GC_BGD(GC_FGD) labels
	{
		bool isb = (flags & BGD_KEY) != 0,
			isf = (flags & FGD_KEY) != 0;
		if (rectState == NOT_SET && !isb && !isf)
		{
			rectState = IN_PROCESS;
			rect = Rect(x, y, 1, 1);
		}
		if ((isb || isf) && rectState == SET)
			lblsState = IN_PROCESS;
	}
	break;
	case EVENT_RBUTTONDOWN: // set GC_PR_BGD(GC_PR_FGD) labels
	{
		bool isb = (flags & BGD_KEY) != 0,
			isf = (flags & FGD_KEY) != 0;
		if ((isb || isf) && rectState == SET)
			prLblsState = IN_PROCESS;
	}
	break;
	case EVENT_LBUTTONUP:
		if (rectState == IN_PROCESS)
		{
			rect = Rect(Point(rect.x, rect.y), Point(x, y));
			rectState = SET;
			setRectInMask();
			CV_Assert(bgdPxls.empty() && fgdPxls.empty() && prBgdPxls.empty() && prFgdPxls.empty());
			showImage();
		}
		if (lblsState == IN_PROCESS)
		{
			setLblsInMask(flags, Point(x, y), false);
			lblsState = SET;
			showImage();
		}
		break;
	case EVENT_RBUTTONUP:
		if (prLblsState == IN_PROCESS)
		{
			setLblsInMask(flags, Point(x, y), true);
			prLblsState = SET;
			showImage();
		}
		break;
	case EVENT_MOUSEMOVE:
		if (rectState == IN_PROCESS)
		{
			rect = Rect(Point(rect.x, rect.y), Point(x, y));
			CV_Assert(bgdPxls.empty() && fgdPxls.empty() && prBgdPxls.empty() && prFgdPxls.empty());
			showImage();
		}
		else if (lblsState == IN_PROCESS)
		{
			setLblsInMask(flags, Point(x, y), false);
			showImage();
		}
		else if (prLblsState == IN_PROCESS)
		{
			setLblsInMask(flags, Point(x, y), true);
			showImage();
		}
		break;
	}
}

int GCApplication::nextIter()
{
	if (isInitialized)
		grabCut(*image, mask, rect, bgdModel, fgdModel, 1);
	else
	{
		if (rectState != SET)
			return iterCount;

		if (lblsState == SET || prLblsState == SET)
			grabCut(*image, mask, rect, bgdModel, fgdModel, 1, GC_INIT_WITH_MASK);
		else
			grabCut(*image, mask, rect, bgdModel, fgdModel, 1, GC_INIT_WITH_RECT);

		isInitialized = true;
	}
	iterCount++;

	bgdPxls.clear(); fgdPxls.clear();
	prBgdPxls.clear(); prFgdPxls.clear();

	return iterCount;
}

GCApplication gcapp;

static void on_mouse(int event, int x, int y, int flags, void* param)
{
	gcapp.mouseClick(event, x, y, flags, param);
}

int main(int argc, char** argv)
{
	cv::CommandLineParser parser(argc, argv, "{@input| messi5.jpg |}");
	help(argv);

	string filename = parser.get<string>("@input");
	if (filename.empty())
	{
		cout << "\nDurn, empty filename" << endl;
		return 1;
	}
	Mat image = imread(samples::findFile(filename), IMREAD_COLOR);
	if (image.empty())
	{
		cout << "\n Durn, couldn't read image filename " << filename << endl;
		return 1;
	}

	const string winName = "image";
	namedWindow(winName, WINDOW_AUTOSIZE);
	setMouseCallback(winName, on_mouse, 0);

	gcapp.setImageAndWinName(image, winName);
	gcapp.showImage();

	for (;;)
	{
		char c = (char)waitKey(0);
		switch (c)
		{
		case '\x1b':
			cout << "Exiting ..." << endl;
			goto exit_main;
		case 'r':
			cout << endl;
			gcapp.reset();
			gcapp.showImage();
			break;
		case 'n':
			int iterCount = gcapp.getIterCount();
			cout << "<" << iterCount << "... ";
			int newIterCount = gcapp.nextIter();
			if (newIterCount > iterCount)
			{
				gcapp.showImage();
				cout << iterCount << ">" << endl;
			}
			else
				cout << "rect must be determined>" << endl;
			break;
		}
	}

exit_main:
	destroyWindow(winName);
	return 0;
}

结果