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 toGC_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 andGC_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 checkswitch( 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 );elsegrabCut( *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;}elsecout << "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