| OpenCV 5.0.0alpha Open Source Computer Vision

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samples/cpp/snippets/segment_objects.cpp

An example using drawContours to clean up a background segmentation result

#include "opencv2/imgproc.hpp"
#include "opencv2/videoio.hpp"
#include "opencv2/highgui.hpp"
#include "opencv2/video/background_segm.hpp"
#include <stdio.h>
#include <string>
using namespace std;
using namespace cv;
static void help(char** argv)
{
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"
"%s [video file, else it reads camera 0]\n\n", argv[0]);
}
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)
{
VideoCapture cap;
bool update_bg_model = true;
CommandLineParser parser(argc, argv, "{help h||}{@input||}");
if (parser.has("help"))
{
help(argv);
return 0;
}
string input = parser.get<std::string>("@input");
if (input.empty())
cap.open(0);
else
cap.open(samples::findFileOrKeep(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);
Ptr<BackgroundSubtractorMOG2> bgsubtractor=createBackgroundSubtractorMOG2();
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;
}
background_segm.hpp
cv::CommandLineParser
Designed for command line parsing.
Definition utility.hpp:890
cv::Mat
n-dimensional dense array class
Definition mat.hpp:951
cv::Mat::size
MatSize size
Definition mat.hpp:2448
cv::Mat::empty
bool empty() const
Returns true if the array has no elements.
cv::Point_< int >
cv::Scalar_< double >
cv::VideoCapture
Class for video capturing from video files, image sequences or cameras.
Definition videoio.hpp:727
cv::VideoCapture::open
virtual bool open(const String &filename, int apiPreference=CAP_ANY)
Opens a video file or a capturing device or an IP video stream for video capturing.
cv::VideoCapture::isOpened
virtual bool isOpened() const
Returns true if video capturing has been initialized already.
cv::Ptr
std::shared_ptr< _Tp > Ptr
Definition cvstd_wrapper.hpp:23
CV_8UC3
#define CV_8UC3
Definition interface.h:101
cv::imshow
void imshow(const String &winname, InputArray mat)
Displays an image in the specified window.
cv::waitKey
int waitKey(int delay=0)
Waits for a pressed key.
cv::namedWindow
void namedWindow(const String &winname, int flags=WINDOW_AUTOSIZE)
Creates a 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::createBackgroundSubtractorMOG2
Ptr< BackgroundSubtractorMOG2 > createBackgroundSubtractorMOG2(int history=500, double varThreshold=16, bool detectShadows=true)
Creates MOG2 Background Subtractor.
highgui.hpp
main
int main(int argc, char *argv[])
Definition highgui_qt.cpp:3
imgproc.hpp
cv
Definition core.hpp:107
std
STL namespace.
videoio.hpp