OpenCV  3.2.0
Open Source Computer Vision
segment_objects.cpp

An example using drawContours to clean up a background segmentation result

#include <stdio.h>
#include <string>
using namespace std;
using namespace cv;
static void help()
{
printf("\n"
"This program demonstrated a simple method of connected components clean up of background subtraction\n"
"When the program starts, it begins learning the background.\n"
"You can toggle background learning on and off by hitting the space bar.\n"
"Call\n"
"./segment_objects [video file, else it reads camera 0]\n\n");
}
static void refineSegments(const Mat& img, Mat& mask, Mat& dst)
{
int niters = 3;
vector<vector<Point> > contours;
vector<Vec4i> hierarchy;
Mat temp;
dilate(mask, temp, Mat(), Point(-1,-1), niters);
erode(temp, temp, Mat(), Point(-1,-1), niters*2);
dilate(temp, temp, Mat(), Point(-1,-1), niters);
findContours( temp, contours, hierarchy, RETR_CCOMP, CHAIN_APPROX_SIMPLE );
dst = Mat::zeros(img.size(), CV_8UC3);
if( contours.size() == 0 )
return;
// iterate through all the top-level contours,
// draw each connected component with its own random color
int idx = 0, largestComp = 0;
double maxArea = 0;
for( ; idx >= 0; idx = hierarchy[idx][0] )
{
const vector<Point>& c = contours[idx];
double area = fabs(contourArea(Mat(c)));
if( area > maxArea )
{
maxArea = area;
largestComp = idx;
}
}
Scalar color( 0, 0, 255 );
drawContours( dst, contours, largestComp, color, FILLED, LINE_8, hierarchy );
}
int main(int argc, char** argv)
{
bool update_bg_model = true;
CommandLineParser parser(argc, argv, "{help h||}{@input||}");
if (parser.has("help"))
{
help();
return 0;
}
string input = parser.get<std::string>("@input");
if (input.empty())
cap.open(0);
else
cap.open(input);
if( !cap.isOpened() )
{
printf("\nCan not open camera or video file\n");
return -1;
}
Mat tmp_frame, bgmask, out_frame;
cap >> tmp_frame;
if(tmp_frame.empty())
{
printf("can not read data from the video source\n");
return -1;
}
namedWindow("video", 1);
namedWindow("segmented", 1);
bgsubtractor->setVarThreshold(10);
for(;;)
{
cap >> tmp_frame;
if( tmp_frame.empty() )
break;
bgsubtractor->apply(tmp_frame, bgmask, update_bg_model ? -1 : 0);
refineSegments(tmp_frame, bgmask, out_frame);
imshow("video", tmp_frame);
imshow("segmented", out_frame);
char keycode = (char)waitKey(30);
if( keycode == 27 )
break;
if( keycode == ' ' )
{
update_bg_model = !update_bg_model;
printf("Learn background is in state = %d\n",update_bg_model);
}
}
return 0;
}
imgproc.hpp
cv::RETR_CCOMP
@ RETR_CCOMP
Definition: imgproc.hpp:434
cv::FILLED
@ FILLED
Definition: core.hpp:215
cv::BackgroundSubtractor::apply
virtual void apply(InputArray image, OutputArray fgmask, double learningRate=-1)=0
Computes a foreground mask.
cv::erode
void erode(InputArray src, OutputArray dst, InputArray kernel, Point anchor=Point(-1,-1), int iterations=1, int borderType=BORDER_CONSTANT, const Scalar &borderValue=morphologyDefaultBorderValue())
Erodes an image by using a specific structuring element.
cv::VideoCapture
Class for video capturing from video files, image sequences or cameras.
Definition: videoio.hpp:597
cv::waitKey
int waitKey(int delay=0)
Waits for a pressed key.
highgui.hpp
cv::namedWindow
void namedWindow(const String &winname, int flags=WINDOW_AUTOSIZE)
Creates a window.
cv::Scalar_< double >
background_segm.hpp
cv::LINE_8
@ LINE_8
8-connected line
Definition: core.hpp:217
cv::dilate
void dilate(InputArray src, OutputArray dst, InputArray kernel, Point anchor=Point(-1,-1), int iterations=1, int borderType=BORDER_CONSTANT, const Scalar &borderValue=morphologyDefaultBorderValue())
Dilates an image by using a specific structuring element.
CV_8UC3
#define CV_8UC3
Definition: interface.h:84
cv::contourArea
double contourArea(InputArray contour, bool oriented=false)
Calculates a contour area.
cv::Mat::size
MatSize size
Definition: mat.hpp:1978
cv::createBackgroundSubtractorMOG2
Ptr< BackgroundSubtractorMOG2 > createBackgroundSubtractorMOG2(int history=500, double varThreshold=16, bool detectShadows=true)
Creates MOG2 Background Subtractor.
cv::Ptr
Template class for smart pointers with shared ownership.
Definition: cvstd.hpp:281
cv::VideoCapture::isOpened
virtual bool isOpened() const
Returns true if video capturing has been initialized already.
cv::VideoCapture::open
virtual bool open(const String &filename)
Open video file or a capturing device or a IP video stream for video capturing.
cv::imshow
void imshow(const String &winname, InputArray mat)
Displays an image in the specified window.
cv::drawContours
void drawContours(InputOutputArray image, InputArrayOfArrays contours, int contourIdx, const Scalar &color, int thickness=1, int lineType=LINE_8, InputArray hierarchy=noArray(), int maxLevel=INT_MAX, Point offset=Point())
Draws contours outlines or filled contours.
cv::Point
Point2i Point
Definition: types.hpp:183
cv::BackgroundSubtractorMOG2::setVarThreshold
virtual void setVarThreshold(double varThreshold)=0
Sets the variance threshold for the pixel-model match.
cv::Mat
n-dimensional dense array class
Definition: mat.hpp:741
cv::CommandLineParser
Designed for command line parsing.
Definition: utility.hpp:735
cv
Definition: affine.hpp:52
cv::CHAIN_APPROX_SIMPLE
@ CHAIN_APPROX_SIMPLE
Definition: imgproc.hpp:448
cv::findContours
void findContours(InputOutputArray image, OutputArrayOfArrays contours, OutputArray hierarchy, int mode, int method, Point offset=Point())
Finds contours in a binary image.
videoio.hpp