Having two thread, one product data, another one process data. The data is not just an int or float but a complex object. In my case, it's an OpenCV Mat(an image). If the first thread only created half-size of the image, and second thread read it, will get half size of the image? The image will be broken?
int main(int argc, char *argv[])
{
cv::Mat buffer;
cv::VideoCapture cap;
std::mutex mutex;
cap.open(0);
std::thread product([](cv::Mat& buffer, cv::VideoCapture cap, std::mutex& mutex){
while (true) { // keep product the new image
cv::Mat tmp;
cap >> tmp;
//mutex.lock();
buffer = tmp.clone();
//mutex.unlock();
}
}, std::ref(buffer), cap, std::ref(mutex));
product.detach();
int i;
while (true) { // process in the main thread
//mutex.lock();
cv::Mat tmp = buffer;
//mutex.unlock();
if(!tmp.data)
std::cout<<"null"<<i++<<std::endl;
else {
//std::cout<<"not null"<<std::endl;
cv::imshow("test", tmp);
}
if(cv::waitKey(30) >= 0) break;
}
return 0;
}
Do I need to add a mutex around write and read to make sure the image not be broken? Like this:
int main(int argc, char *argv[])
{
cv::Mat buffer;
cv::VideoCapture cap;
std::mutex mutex;
cap.open(0);
std::thread product([](cv::Mat& buffer, cv::VideoCapture cap, std::mutex& mutex){
while (true) { // keep product the new image
cv::Mat tmp;
cap >> tmp;
mutex.lock();
buffer = tmp.clone();
mutex.unlock();
}
}, std::ref(buffer), cap, std::ref(mutex));
product.detach();
while (true) { // process in the main thread
mutex.lock();
cv::Mat tmp = buffer;
mutex.unlock();
if(!tmp.data)
std::cout<<"null"<<std::endl;
else {
std::cout<<"not null"<<std::endl;
cv::imshow("test", tmp);
}
}
return 0;
}
This question related to How to solves image processing cause camera io delay?
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