Can anyone tell me what's wrong with my code? I can use my webcam by other code, so there is nothing do with the supported problem. In my code below, I must set the camera index into a loop so that i can motivate my camera(the led inductor is on, simply set "CvCapture* camera=cvCaptureFromCAM(0)" can not run! that's wierd!).However, I just can obtain a greysreen,why?
#include "highgui.h"
#include "cv.h"
int main(int grac, char** grav)
{
CvCapture* camera;
int index;
for (index = -1; index <1; index++)
{
camera = cvCaptureFromCAM(index);
if (camera)
{
printf("%d\n", index);
IplImage* f;
cvNamedWindow("camera", CV_WINDOW_AUTOSIZE);
while (1)
{
f = cvQueryFrame(camera);
cvShowImage("camera", f);
char c = cvWaitKey(33);
if (c == 27)break;
}
}
}
cvReleaseCapture(&camera);
cvDestroyAllWindows;
}
Related
The code is:
#include <iostream>
#include <opencv2/opencv.hpp>
int main (int argc, char** argv) {
auto path = "C:/Users/huhua/Pictures/11.jpg";
auto img = cv::imread(path);
if (img.empty()) {
std::cout << "is empty" << std::endl;
return 1;
}
cv::imshow("demo", img);
cv::waitKey(0);
return 0;
}
The 11.jpg exist. And if I use another 11.bmp. It works well.
After debug. The error is throw at libjpeg-trubo/src/jdatasr.c
fill_input_buffer(j_decompress_ptr cinfo)
{
my_src_ptr src = (my_src_ptr)cinfo->src;
size_t nbytes;
// error is throw at here
nbytes = JFREAD(src->infile, src->buffer, INPUT_BUF_SIZE);
// ...
}
Is my libjpeg issue??
How to fix this?
The 11.jpg image:
Update:
The OpenCV info
Update on 2021/10/19:
The reason is I set the cmake_toolchain_path after project(xxx). I should set the cmake_toolchain_path before project.
https://github.com/microsoft/vcpkg/discussions/20802
When i set the position and velocities of the joints in the trajectory msgs i got an error: \
[state_publisher-2] process has died [pid 13362, exit code -11, cmd /home/rob/catkin_ws/devel/lib/r2d2/state_publisher __name:=state_publisher __log:=/home/rob/.ros/log/9980f352-cf74-11e6-8644-d4c9efe8bd37/state_publisher-2.log].
log file: /home/rob/.ros/log/9980f352-cf74-11e6-8644-d4c9efe8bd37/state_publisher-2*.log
My ros node to send geometry_msgs is:
#include <string>
#include <ros/ros.h>
#include <sensor_msgs/JointState.h>
#include <tf/transform_broadcaster.h>
#include <trajectory_msgs/JointTrajectory.h>
#include <vector>
int main(int argc, char** argv) {
ros::init(argc, argv, "state_publisher");
ros::NodeHandle n;
ros::Publisher joint_pub = n.advertise<trajectory_ms
gs::JointTrajectory>("set_joint_trajectory", 1);
ros::Rate loop_rate(30);
const double degree = M_PI/180;
// robot state
double tilt = 0, tinc = degree, swivel=0, angle=0, height=0, hinc=0.005;
// message declarations
trajectory_msgs::JointTrajectory joint_state;
std::vector<trajectory_msgs::JointTrajectoryPoint> points_n(3);
points_n[0].positions[0] = 1; points_n[0].velocities[0]=10;
while (ros::ok()) {
//update joint_state
joint_state.header.stamp = ros::Time::now();
joint_state.joint_names.resize(3);
joint_state.points.resize(3);
joint_state.joint_names[0] ="swivel";
joint_state.points[0] = points_n[0];
joint_state.joint_names[1] ="tilt";
joint_state.points[1] = points_n[1];
joint_state.joint_names[2] ="periscope";
joint_state.points[2] = points_n[2];
joint_pub.publish(joint_state);
// This will adjust as needed per iteration
loop_rate.sleep();
}
return 0;
}
Here when i donot set the position and velocity value it runs without error and when i run rostopic echo /set_joint_trajectory i can clearly see the outputs as all the parameters of points is 0. I also tried below program but it published nothing:
#include <string>
#include <ros/ros.h>
#include <sensor_msgs/JointState.h>
#include <tf/transform_broadcaster.h>
#include <trajectory_msgs/JointTrajectory.h>
#include <vector>
int main(int argc, char** argv) {
ros::init(argc, argv, "state_publisher");
ros::NodeHandle n;
ros::Publisher joint_pub = n.advertise<trajectory_msgs::JointTrajectory>("set_joint_trajectory", 1);
trajectory_msgs::JointTrajectory joint_state;
joint_state.header.stamp = ros::Time::now();
joint_state.header.frame_id = "camera_link";
joint_state.joint_names.resize(3);
joint_state.points.resize(3);
joint_state.joint_names[0] ="swivel";
joint_state.joint_names[1] ="tilt";
joint_state.joint_names[2] ="periscope";
size_t size = 2;
for(size_t i=0;i<=size;i++) {
trajectory_msgs::JointTrajectoryPoint points_n;
int j = i%3;
points_n.positions.push_back(j);
points_n.positions.push_back(j+1);
points_n.positions.push_back(j*2);
joint_state.points.push_back(points_n);
joint_state.points[i].time_from_start = ros::Duration(0.01);
}
joint_pub.publish(joint_state);
ros::spinOnce();
return 0;
}
You are accessing points_n[0].positions[0] and points_n[0].velocities[0] without allocating the memory for positions and velocities. Use
...
// message declarations
trajectory_msgs::JointTrajectory joint_state;
std::vector<trajectory_msgs::JointTrajectoryPoint> points_n(3);
points_n[0].positions.resize(1);
points_n[0].velocities.resize(1);
...
then set the values or use points_n[0].positions.push_back(...) instead. The same applies to points_n[1] and points_n[2].
In your second example it looks like your program terminates before anything is sent. Try to publish repeatedly in a while-loop with
while(ros::ok()){
...
ros::spinOnce();
}
All examples and books I've seen so far recommends using waitKey(1) to force repaint OpenCV window. That looks weird and too hacky. Why wait for even 1ms when you don't have to?
Are there any alternatives? I tried cv::updateWindow but it seems to require OpenGL and therefore crashes. I'm using VC++ on Windows.
I looked in to source and as #Dan Masek said, there doesn't seem to be any other functions to process windows message. So I ended up writing my own little DoEvents() function for VC++. Below is the full source code that uses OpenCV to display video frame by frame while skipping desired number of frames.
#include <windows.h>
#include <iostream>
#include "opencv2/opencv.hpp"
using namespace cv;
using namespace std;
bool DoEvents();
int main(int argc, char *argv[])
{
VideoCapture cap(argv[1]);
if (!cap.isOpened())
return -1;
namedWindow("tree", CV_GUI_EXPANDED | CV_WINDOW_AUTOSIZE);
double frnb(cap.get(CV_CAP_PROP_FRAME_COUNT));
std::cout << "frame count = " << frnb << endl;
for (double fIdx = 0; fIdx < frnb; fIdx += 50) {
Mat frame;
cap.set(CV_CAP_PROP_POS_FRAMES, fIdx);
bool success = cap.read(frame);
if (!success) {
cout << "Cannot read frame " << endl;
break;
}
imshow("tree", frame);
if (!DoEvents())
return 0;
}
return 0;
}
bool DoEvents()
{
MSG msg;
BOOL result;
while (::PeekMessage(&msg, NULL, 0, 0, PM_NOREMOVE))
{
result = ::GetMessage(&msg, NULL, 0, 0);
if (result == 0) // WM_QUIT
{
::PostQuitMessage(msg.wParam);
return false;
}
else if (result == -1)
return true; //error occured
else
{
::TranslateMessage(&msg);
::DispatchMessage(&msg);
}
}
return true;
}
I am trying to use CodeBook method for OpenCV to subtract the background. So far so good, but I am not sure if I can update the codebook for moving objects after some time span, say 5 minutes, I need to update the codebook after which I get lots of moving objects. How do I make sure that after 5 minutes I have a background that needs to be updated?
Thanks for the tips!
kim's algorithm supposedly has a cache layer, i did not dig deep enough into opencv implementation to know how to have a workable version that works with exposure problem.
notes
opencv book(which i havent read) should have the info you need if it's there at all
this is only 1 channel and not in yuv although it can be extended
needs more work on speed/testing (you can of course turn on optimization in compiler)
background subtraction is a buzzy word. try "change detection"
bgfg_cb.h
#ifndef __bgfg_cb_h__
#define __bgfg_cb_h__
//http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.148.9778&rep=rep1&type=pdf
#include "opencv2/core/core.hpp"
#include "opencv2/imgproc/imgproc.hpp"
#include "opencv2/highgui/highgui.hpp"
#include <iostream>
#include <time.h>
using namespace cv;
using namespace std;
struct codeword {
float min;
float max;
float f;
float l;
int first;
int last;
bool isStale;
};
extern int alpha ;
extern float beta ;
extern int Tdel ,Tadd , Th;
void initializeCodebook(int w,int h);
void update_cb(Mat& frame);
void fg_cb(Mat& frame,Mat& fg);
#endif
bgfg_cb.cpp
#include "opencv2/core/core.hpp"
#include "opencv2/imgproc/imgproc.hpp"
#include "opencv2/highgui/highgui.hpp"
#include <iostream>
#include <time.h>
#include "bgfg_cb.h"
using namespace cv;
using namespace std;
vector<codeword> **cbMain;
vector<codeword> **cbCache;
int t=0;
int alpha = 10;//knob
float beta =1;
int Tdel = 200,Tadd = 150, Th= 200;//knobs
void initializeCodebook(int w,int h)
{
cbMain = new vector<codeword>*[w];
for(int i = 0; i < w; ++i)
cbMain[i] = new vector<codeword>[h];
cbCache = new vector<codeword>*[w];
for(int i = 0; i < w; ++i)
cbCache[i] = new vector<codeword>[h];
}
void update_cb(Mat& frame)
{
if(t>10) return;
for(int i=0;i<frame.rows;i++)
{
for(int j=0;j<frame.cols;j++)
{
int pix = frame.at<uchar>(i,j);
vector<codeword>& cm =cbMain[i][j];
bool found = false;
for(int k=0;k<cm.size();k++)
{
if(cm[k].min<=pix && pix<=cm[k].max && !found)
{
found=true;
cm[k].min = ((pix-alpha)+(cm[k].f*cm[k].min))/(cm[k].f+1);
cm[k].max = ((pix+alpha)+(cm[k].f*cm[k].max))/(cm[k].f+1);
cm[k].l=0;
cm[k].last=t;
cm[k].f++;
}else
{
cm[k].l++;
}
}
if(!found)
{
codeword n={};
n.min=max(0,pix-alpha);
n.max=min(255,pix+alpha);
n.f=1;
n.l=0;
n.first=t;
n.last=t;
cm.push_back(n);
}
}
}
t++;
}
void fg_cb(Mat& frame,Mat& fg)
{
fg=Mat::zeros(frame.size(),CV_8UC1);
if(cbMain==0) initializeCodebook(frame.rows,frame.cols);
if(t<10)
{
update_cb(frame);
return;
}
for(int i=0;i<frame.rows;i++)
{
for(int j=0;j<frame.cols;j++)
{
int pix = frame.at<uchar>(i,j);
vector<codeword>& cm = cbMain[i][j];
bool found = false;
for(int k=0;k<cm.size();k++)
{
if(cm[k].min<=pix && pix<=cm[k].max && !found)
{
cm[k].min = ((1-beta)*(pix-alpha)) + (beta*cm[k].min);
cm[k].max = ((1-beta)*(pix+alpha)) + (beta*cm[k].max);
cm[k].l=0;
cm[k].first=t;
cm[k].f++;
found=true;
}else
{
cm[k].l++;
}
}
cm.erase( remove_if(cm.begin(), cm.end(), [](codeword& c) { return c.l>=Tdel;} ), cm.end() );
fg.at<uchar>(i,j) = found?0:255;
if(found) continue;
found = false;
vector<codeword>& cc = cbCache[i][j];
for(int k=0;k<cc.size();k++)
{
if(cc[k].min<=pix && pix<=cc[k].max && !found)
{
cc[k].min = ((1-beta)*(pix-alpha)) + (beta*cc[k].min);
cc[k].max = ((1-beta)*(pix+alpha)) + (beta*cc[k].max);
cc[k].l=0;
cc[k].first=t;
cc[k].f++;
found=true;
}else
{
cc[k].l++;
}
}
if(!found)
{
codeword n={};
n.min=max(0,pix-alpha);
n.max=min(255,pix+alpha);
n.f=1;
n.l=0;
n.first=t;
n.last=t;
cc.push_back(n);
}
cc.erase( remove_if(cc.begin(), cc.end(), [](codeword& c) { return c.l>=Th;} ), cc.end() );
for(vector<codeword>::iterator it=cc.begin();it!=cc.end();it++)
{
if(it->f>Tadd)
{
cm.push_back(*it);
}
}
cc.erase( remove_if(cc.begin(), cc.end(), [](codeword& c) { return c.f>Tadd;} ), cc.end() );
}
}
}
main.cpp
#include "opencv2/core/core.hpp"
#include "opencv2/imgproc/imgproc.hpp"
#include "opencv2/highgui/highgui.hpp"
#include "bgfg_cb.h"
#include <iostream>
using namespace cv;
using namespace std;
void proc()
{
Mat frame,fg,gray;
VideoCapture cap("C:/Downloads/S2_L1.tar/S2_L1/Crowd_PETS09/S2/L1/Time_12-34/View_001/frame_%04d.jpg");
cap >> frame;
initializeCodebook(frame.rows,frame.cols);
for(;;)
{
cap>>frame;
cvtColor(frame,gray,CV_BGR2GRAY);
fg_cb(gray,fg);
Mat cc;
imshow("fg",fg);
waitKey(1);
}
}
int main(int argc, char ** argv)
{
proc();
cin.ignore(1);
return 0;
}
i am still new on opencv, i make simple program based on sample to access webcam but always fails. i change variable id to 0,1,2...100 but i got same result. this is my program:
#include "cv.h"
#include "highgui.h"
#include "stdio.h"
#include "iostream"
// A Simple Camera Capture Framework
int main()
{
IplImage* img = NULL;
CvCapture* cap = NULL;
int id=0;
cap = cvCaptureFromCAM(id);
cvNamedWindow("Images",CV_WINDOW_AUTOSIZE);
if ( !cap )
printf("ERROR\n\n");
else
for(;;)
{
img = cvQueryFrame(cap);
cvShowImage("Imagenes", img);
cvWaitKey(10);
}
cvReleaseImage(&img);
cvReleaseCapture(&cap);
return 0;
}
thank you for your help
Do yourself a favor and check the return of the functions. Maybe some of them are failing and you'll never know why.
Another tip: try with id = -1.
#include <iostream>
#include <sstream>
#include <string>
#include <cv.h>
#include <highgui.h>
int main()
{
CvCapture* capture = NULL;
if ((capture = cvCaptureFromCAM(-1)) == NULL)
{
fprintf(stderr, "ERROR: capture is NULL \n");
return -1;
}
cvNamedWindow("mywindow", CV_WINDOW_AUTOSIZE);
cvQueryFrame(capture); // Sometimes needed to get correct data
IplImage* frame = NULL;
while (1)
{
if ((frame = cvQueryFrame(capture)) == NULL)
{
fprintf( stderr, "ERROR: cvQueryFrame failed\n");
break;
}
if (frame == NULL)
{
usleep(100000);
continue;
}
cvShowImage("mywindow", frame); // Do not release the frame!
int key = cvWaitKey(10);
if (key == 27) // ESC was pressed
break;
}
cvReleaseCapture(&capture);
cvDestroyWindow("mywindow");
return 0;
}