学习OpenCV——grabcut

 

GrabCut函数说明

Parameters:

image – Input 8-bit 3-channel image. mask – Input/output 8-bit single-channel mask. The mask is initialized by the function whenmode is set to GC_INIT_WITH_RECT. Its elements may have one of following values: GC_BGD defines an obvious background pixels. GC_FGD defines an obvious foreground (object) pixel. GC_PR_BGD defines a possible background pixel. GC_PR_BGD defines a possible foreground pixel. rect – ROI containing a segmented object. The pixels outside of the ROI are marked as “obvious background”. The parameter is only used whenmode==GC_INIT_WITH_RECT . bgdModel – Temporary array for the background model. Do not modify it while you are processing the same image. fgdModel – Temporary arrays for the foreground model. Do not modify it while you are processing the same image. iterCount – Number of iterations the algorithm should make before returning the result. Note that the result can be refined with further calls withmode==GC_INIT_WITH_MASK ormode==GC_EVAL . mode – Operation mode that could be one of the following: GC_INIT_WITH_RECT The function initializes the state and the mask using the provided rectangle. After that it runsiterCount iterations of the algorithm. GC_INIT_WITH_MASK The function initializes the state using the provided mask. Note thatGC_INIT_WITH_RECT and GC_INIT_WITH_MASK can be combined. Then, all the pixels outside of the ROI are automatically initialized withGC_BGD . GC_EVAL The value means that the algorithm should just resume.

函数原型：
    void cv::grabCut( const Mat& img, Mat& mask, Rect rect,
             Mat& bgdModel, Mat& fgdModel,
             int iterCount, int mode )
其中：
img——待分割的源图像，必须是8位3通道（CV_8UC3）图像，在处理的过程中不会被修改；
mask——掩码图像，如果使用掩码进行初始化，那么mask保存初始化掩码信息；在执行分割的时候，也可以将用户交互所设定的前景与背景保存到mask中，然后再传入grabCut函数；在处理结束之后，mask中会保存结果。mask只能取以下四种值：
GCD_BGD（=0），背景；
GCD_FGD（=1），前景；
GCD_PR_BGD（=2），可能的背景；
GCD_PR_FGD（=3），可能的前景。
如果没有手工标记GCD_BGD或者GCD_FGD，那么结果只会有GCD_PR_BGD或GCD_PR_FGD；
rect——用于限定需要进行分割的图像范围，只有该矩形窗口内的图像部分才被处理；
bgdModel——背景模型，如果为null，函数内部会自动创建一个bgdModel；bgdModel必须是单通道浮点型（CV_32FC1）图像，且行数只能为1，列数只能为13x5；
fgdModel——前景模型，如果为null，函数内部会自动创建一个fgdModel；fgdModel必须是单通道浮点型（CV_32FC1）图像，且行数只能为1，列数只能为13x5；
iterCount——迭代次数，必须大于0；
mode——用于指示grabCut函数进行什么操作，可选的值有：
GC_INIT_WITH_RECT（=0），用矩形窗初始化GrabCut；
GC_INIT_WITH_MASK（=1），用掩码图像初始化GrabCut；
GC_EVAL（=2），执行分割。

 

OpenCV自带的代码：

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

#include <iostream>

using namespace std;
using namespace cv;

void help()
{
	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"
		"./grabcut <image_name>\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 CG_FGD pixels\n"
		"\n"
		"\tCTRL+right mouse button - set GC_PR_BGD pixels\n"
		"\tSHIFT+right mouse button - set CG_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 = CV_EVENT_FLAG_CTRLKEY;
const int FGD_KEY = CV_EVENT_FLAG_SHIFTKEY;

void getBinMask( const Mat& comMask, Mat& binMask )
{
	if( comMask.empty() || comMask.type()!=CV_8UC1 )
		CV_Error( CV_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()
{
	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 CV_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 CV_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 CV_EVENT_LBUTTONUP:
		if( rectState == IN_PROCESS )
		{
			rect = Rect( Point(rect.x, rect.y), Point(x,y) );
			rectState = SET;
			setRectInMask();
			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 CV_EVENT_RBUTTONUP:
		if( prLblsState == IN_PROCESS )
		{
			setLblsInMask(flags, Point(x,y), true);
			prLblsState = SET;
			showImage();
		}
		break;
	case CV_EVENT_MOUSEMOVE:
		if( rectState == IN_PROCESS )
		{
			rect = Rect( Point(rect.x, rect.y), Point(x,y) );
			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;

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 )
{
	if( argc!=2 )
	{
		help();
		return 1;
	}
	string filename = argv[1];
	if( filename.empty() )
	{
		cout << "\nDurn, couldn't read in " << argv[1] << endl;
		return 1;
	}
	Mat image = imread( filename, 1 );
	if( image.empty() )
	{
		cout << "\n Durn, couldn't read image filename " << filename << endl;
		return 1;
	}

	help();

	const string winName = "image";
	cvNamedWindow( winName.c_str(), CV_WINDOW_AUTOSIZE );
	cvSetMouseCallback( winName.c_str(), on_mouse, 0 );

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

	for(;;)
	{
		int c = cvWaitKey(0);
		switch( (char) 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:
	cvDestroyWindow( winName.c_str() );
	return 0;
}

参考： http://www.cnblogs.com/xrwang/archive/2010/04/27/GrabCut.html