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