Opencv imshow multiple threads

Opencv imshow multiple threads. It seems like (as I guess) Cv2 cannot be used in multiple threads, eg, one thread create NamedWindow, another thread ImShow. Other than this is a separate thread from the successful imshow of the video file I can’t think of anything else that might be different. jpg"); cv::Mat output(image. Jun 27, 2016 · SumeetB. imshow() function. frame_queue = frame_queue self. I'm using OpenCV (4. getWindowProperty('frame',cv2. I made a opencv c++ program that does a lot of image processing on frames from a video feed and as such decided to implement multithreading to speed things up. edited Dec 6, 2018 at 10:14. When running the code below, the two windows freezes and blacks out. 5. When I run this code, I see just a part of an image. I've defined a 'detect' method as part of a "Detector" class. Mar 13, 2019 · I have multiple threads (one for each camera) that needs to imshow images. waitKey(10) & 0XFF which will auto refresh your screen each 10 milliseconds. Load the Multiple images using cv2. 7 and OpenNI. That’s not quite as good as I would like, but it’s OK. Basically is command line driven, but the input I need really requires a mouse. main. 0. Jul 6, 2018 · In this post, we’ll examine the effect of putting calls to cv2. imread('1. imshow(v_slice[0]) Aug 1, 2021 · The fact that a separate function CreateCameraWindow created the namedWindow cameraWindow and then started the thread in which the cameraWindow was used seems to be the problem. Display image in second thread, OpenCV? 1 OpenCV imshow() in a loop to show image. 3 OpenCV Multi-threading giving errors. uint8) def update_bitmap(): for i in range(512): bitmap[i,i,:] = 128 sleep(1/32) def main(): threading. 9. colRange(0, cols)); image2. Update: I used time. Mar 30, 2019 · opencv's gui functions, like namedWindow, imshow, waitKey HAVE to stay on the main thread. use queues or other sync primitives for that. imshow() infinite loop that is uninterrupted, I have the loop in a thread so the May 5, 2018 · I'm getting a segmentation fault when I try to read and show an image with opencv in Python. To that end, I need to use openCV's imshow() function on the main thread to show frames from separate frame capture and processing threads (since imshow() doesn't work outside it). I need to preview more than one video (actually 2) in multiple threading. subplots(4,1) # use the created array to output your multiple images. Sleep () doesn't work. To capture multiple streams with OpenCV, I recommend using threading which can improve performance by alleviating the heavy I/O operations to a separate thread. Typically you should use cv::namedWindow once before cv::imshow, but normally if you are lazy, cv::imshow can implicitly create that window, BUT: in multiple threads this often doesnt work. Since accessing the webcam/IP/RTSP stream using cv2. 4 so I really didn’t think that was going to be it. Some answers here and at stackoverflow say that mat object has some thread safety, while others say that it's not thread safe. figure() #subplot(r,c) provide the no. What I'm experiencing is a deadlock in the OpenCL code: The code I'm using is multi-threaded and had no issues at all before using the cv::Mat structure. Afterwards, if it still fails on the imshow calls, you'll have to move that to the main thread as well. I'm running a camera thread with another thread. So my . I want to activate GPIO if the object gets detected for 3 seconds while the video is streaming constantly. colRange(0, cols)); Jun 15, 2016 · cv::imshow is a convenience function more suited to prototyping and simple applications. I need to fit the image to the screen. Sep 26, 2017 · Opencv highgui module in windows 10 [closed] opencv imshow causing a memory leak (c++) Regarding imshow (opencv compiled with opengl support) Opencv java - Load image to GUI. avi', 'fourth. type()); cv::parallel_for_(cv::Range(0, image. I am running it on Ubuntu 16. Did I miss anything here? Or do you have a better parctice to do so? Thanks! p. Here is an example, this thread loop is run from a detached thread (use mutex's to lock data passed into the loop and unlock accordingly) Oct 3, 2015 · can you try to call cv::namedWindow("TL") in the main thead before thread creation? If that doesnt work try cv::namedWindow("TL") in the threaded function. 逐次処理版を書く。. You can use these functions to split a program into multiple threads that can execute simultaneously. Let’s see how we can implement our OpenCV and multiprocessing script. from collections import deque. 001) if time Oct 19, 2014 · set mySpacing = 40 //vary this to increase/decrease the gap between the image windows. multithreaded cascade classifire. Import module. py. Option #1: pass a callable to the Thread constructor. So only one sequence of instructions are handled at a time yet you get the illusion of multiple tasks happening because of the halting and running of different threads. These two functions are cv2. Display all the images using cv2. 568280 opencv imshow causing a memory leak (c++) Regarding imshow (opencv compiled with opengl support) imshow without namedWindow showing image. The problem is after a while the cv::imshow("Live") and cv::imshow("ROI") hang up. imshow("img", img); cv2. Without OpenCV ( imshow()) loop works without any Aug 17, 2015 · In this next program, I used multi-processing to background subtract 2 frames ( from 2 different videos ) in parallel. 45. In its own thread, a worker dequeues the png and displays it. Feb 6, 2023 · I then put the frame analysis in a second thread, and the imshow () in a third thread. rows), [&](const cv::Range& range) { Sep 27, 2016 · I have a multi-threading application written in C++ with Qt5. To accomplish this, I built an array with all of my . I have an opencv program where the image processing is sensitive to having a stable and relatively high framerate in the video capture. どう May 19, 2021 · Hi, I have 3 cameras and 3 3070 GPUs on one of my computer. Jan 14, 2016 · 1 1 2. imshow('image',i) This doesn't work for the trivial reason of images requiring a different label, hence this loop would only display the last item in the list. display. I want open more than 2 video files independently I mean by using posix threads . The second argument is optional and specifies the format in which we want the image. read() is a blocking operation, our main program is stuck until the frame is read from the camera device. imread ("autojump. jpg does not show. Measuring changes in performance. 5) When finished processing, each thread grabs the next image from the Oct 10, 2017 · I'm writing some code that will take an image, pass it through a neural network, then return the predictions and bounding boxes from the net back to the main thread. imshow without namedWindow showing image. Here, 7000 ms == 7 secs to show our image windows. asked Dec 23 '19. oni recording file (asus xtion pro live) does some processing and through the Qt signal-slot mechanism pass the frame to the main thread, which display it using imshow(). imshow is a fundamental function in OpenCV, allowing for the visual inspection of images and videos at various stages of image processing or computer vision algorithms. imread("yourimage. jpg') cv2. I'm interested in reading different mat objects from different Oct 19, 2019 · 画像の読み込みを別スレッドにしてみる (OpenCV-Python) 最近はtrioというライブラリを知りました。. 4) Each thread then goes ahead and processes that image. There are 2 classes server. rowRange(rows * 2, 3 * rows). By the way, you can use something like this: image1. Now I am finding out that all calls to a namedWindow have to stay in the same thread that it was created in. colRange(0, cols)); image3. names = ['first. 4 and now to 4. rowRange(rows, 2 * rows). The method looks like this: Mar 12, 2019 · Using threading to handle I/O heavy operations (such as reading frames from a webcam) is a classic programming model. Jul 31, 2021 · But, like I said, this all worked with OCV 2. png") while 1: img=cv2. please find below the code i used Feb 15, 2015 · Draw multiple images in single window is well discussed in another thread OpenCV draw an image over another image. gtk. So, Im trying to re-implement it using multiple threads. Thread(target=update_bitmap). The code is as follow: class Camera(Thread): def __init__(self, cap, frame_queue): super(). imshow('frame', frame0) cv2. And this is where I am stuck. copyTo(dst. A Python script reads png images in from a socket and tries to display then with OpenCV like a slow video. But the time for large disconnection (> = 30s), the program interrupts and ends. cv::cuda::Stream myStream; gpuImage. But when I saw that I could create a new namedWindow Apr 4, 2023 · Basically, I am seeing issue with any pixel value I specify, and I am not seeing an image for CV_16CU3. In run function of the sub-class, I did the following things: while True: read image from camera. imshow('image',self. Very Simple C# Winforms App, OpenCVSharp4, Thread. I have use waitkey() and imshow() in the main thread. Jun 23, 2017 · have you tried creating the video capture and imshow once in the main thread, passing it to the child thread as a reference and then synchronizing access via a mutex or related synchronization primitive? I'm not an OpenCV expert, but there is a lot of what appears to be unnecessary opening/closing of the VideoCapture. waitKey() function, you can provide any value to close the image and continue with further lines of code. May 4, 2023 · I am doing a learning experiment: using a worker thread to do the frame capturing from web cam, then send the frames to the main thread to do a processing which is forwarding to a face detection model (yunet). I’m sure there is something that changed that, once I find it, I can work around it. jpg filenames, and called cv. Since accessing the webcam/camera using cv2. for smoother playback. If I just call function work(), it works! But when I put it into a thread, nothing is displayed. Option #2: Implement a subclass of Thread and override the run method with the code to be run. Dec 21, 2017 · For playing multiple videos, we have to use unique window titles for each video. sleep (). matchTemplate on each sub-image against the base image. width>0 && size. do yolov3 deep learning. All the code used in this post can be found on Github. imshow () Wait for keyboard button press using cv2. and it worked, my cpu usage is 30% now. 1 1 2 3. I installed using: pip3 install opencv-contrib-python The code is only three lines: import cv2 im = cv2. Note that NO_OF_CAMERAS = 2 and I have removed some functions. I tried without Imshow() if there is any issue with another element. 3) Each thread grabs an image from imageQueue, and then erases that image from the vector. Communicate with this displaying thread via a thread-safe queue. You can display an image to the user during the execution of your Python OpenCV application. Keyboard shortcuts: ESC - exit. waitKey(0); cv2. It means imshow () will be called in every thread that the application created. C++: Use the Mat::Mat(const Mat& m, const Range& rowRange, const Range& colRange) constructor to get a cv::Mat pointing to a subimage of your original window, then use the copyTo method to copy your small image into the big one. cap = cap self Jun 16, 2017 · My workaround is to start a thread in python that only deals with opencv named window display. using namespace cv; Now, let's analyze the main code. cap0 = cv2. – Aug 2, 2015 · 画像処理・画像認識のプログラムを書くと、次の画像の先読みをしたくなる。. waitKey () Exit window and destroy all windows using cv2. cv2. import cv2 as cv. start() hz = 30 delta_t = 1 / hz t = time. Apr 16, 2015 · Using the tutorial as an example, capturing images from a single camera is simply: import cv2. I am writing a program that displays a webcam feed live on the computer screen while also taking an image from that feed every 30 seconds or so to do some operation on that image (mainly slicing it up using numpy and opencv and reading numbers with Tesseract). Unfortunately, all the image processing I do is slowing down the framerate significantly, resulting in erroneous behavior in my program. read() and cv2. Run synchronously, the code works perfectly, but slowly due to the large volume of sub-images. destroyAllWindows () Functions Used. def webcam_video(): cap = cv2. You'll need a condition variable for each thread, and global variables which the threads write to and the main thread uses to update the windows. update () — method passed to thread which it runs in the background to read the next available frame. // Crashes with cv_terminate_handler () cv::waitKey (10); Any ideas. I mean blank window appears and when I move mouse cursor, it doesn’t show even co-ordinates. However, if I try to initialize a second camera, attempting to read() from it returns None: import cv2. docs. What happens is that the thread works the very first time, but at the second run the imshow call freezes forever. I had not paid attention to your suggestion at first because this is the way it was working in OpenCV 2. I work with OpenCV functions in a multi-threaded software for decoding/encoding and tracking, and the only issue that I have find so far is with functions from highgui module which deal with windows events such as "cv::imshow" and "cv::waitKey". import cv2. destroyAllWindows(). I disconnected in a short period of time (<30s), it automatically reconnected. Mar 29, 2015 · I am trying to display multi-videos by using multithread with cv::VideoCapture and std::thread. There is some ambiguity about this issue. py file and insert the following code: # import the necessary packages. imshow, so that each thread will generate a different window, and you should place them somewhere distinct so that they aren't appearing one over the other, i just added in index to them so that each distinct index will have a position on screen and different title, also Jun 1, 2023 · if you want to stick with opencv for the imshow, you'll have to funnel all the imshow stuff through a single thread. from multiprocessing. I'm using Mac OS X 10. 1. parallel_hashing import process_images. Its versatility in displaying images and videos makes it an indispensable tool for debugging and understanding the workflow of OpenCV-based applications. I send the frames via queue. The chrCameraBuffer1 is an unsigned char unsigned char * chrCameraBuffer1; Later today, when I get a chance, I will just to a loadImage into mTmpImage and see what happens. I have tried with multithreading (join method) but the video gets paused during the thread call, because it is having time. set myTime = 7000 //in milliseconds. pool import ThreadPool. Mar 20, 2017 · When I leave out the line with cv2. the time needed for this step is around 30ms. When I break the freeze using a break, the program crash. Dec 29, 2019 · Since the algorithm only considers a specific area to calculate the threshold values, I'd like to run each chunk of the image in a seperate thread/process. of rows and columns. It is likely that passing 0 gives the same camera as 1, and you can't connect to the same camera twice. Here’s an example of how to use multi-threading in OpenCV: cv::Mat image = cv::imread("image. This will allow displaying opencv imshow from multiple threads. When I use imshow() for a random picture in another thread, the image could not be shown unless I put waitkey(0) to freeze it. destroyAllWindows() Then if you press Enter on the image, it will successfully close the image and you can proceed running other commands. The image size is 1920 × 1080. imshow ("image",img) k=cv2. - TaegyunHa/CvImshowThread CvImShowThread is a header only class that manages the opencv imshow from the seperate thread. Asked: 2020-09-30 11:21:37 -0600 Seen: 228 times Last updated: Sep 30 '20 Mar 8, 2014 · The cv2. My app depends on multi-threading. をご覧ください。. waitKey (0) & 0XFF if k== 27 : break cv2. First, I successfully connected and displayed the IP camera via RTSP. 1. imshow() in their own dedicated threads. +50. 2, Opencv 2. 643×557 8. VideoCapture(). I knew that waitKey (ms) also needs to be called following by imshow (). Dec 27, 2014 · The frames from the camera will be captured in a thread. Python + Trio の非同期コーディングパターン. imshow namedWindow crash Aug 1, 2021 · I am porting from Windows C++ VS2017 OpenCV 2. 10. camera and computer are both in the same local LAN. Jan 13, 2016 · In python is really easy, define a lock in your code and add in the run method of your thread: with image_lock: cv2. Each thread captures a video and display each frame of the video with imshow till the end. Another idea would be to display the images in a separate thread, and maybe even intentionally reduce the frame rate, skip every other image, for example. But this simple code below is still confusing. I need help. waitKey() and cv2. " So you may need to do 1 and 2. imread () Concatenate the images using concatenate (), with axis value provided as per orientation requirement. With Android, how do I pass control back to the main thread? [closed] openmp and thread with opencv. -- in a GUI with a proper GUI toolkit, everything (events/signals/data) is passed around between threads anyway, and concurrent access is either guarded, or there is no concurrent access and it's all turned into events that go in an Mar 29, 2017 · To fix it, you must move all the namedWindow calls to the main thread. Here is a sample code demonstrating how it can be achieved. I've read that cv2. Jun 24, 2016 · 3. Hello, I had a problem when I started getting to know OpenCV in C ++. cpp. waitKey(0) & 0XFF to k=cv2. Dec 6, 2014 · The problem is that processing each frame takes a bit of time, and this results in delay because the imshow() method grabs the topmost frame in the queue, but at the time of displaying the frame is "old". However, when I run more than one thread, I get Gtk errors. py receives a raw png from a socket and places it on queue. f, axarr = plt. Copy your images into the big image. destroyAllWindows () The image Aug 10, 2020 · I wanted to run one multithread along with opencv video stream. '''. It has a main thread that starts a second thread which capture frame from a . You can try alternatives such as Qt and glfw. GPU HOUGH in multithreading applications Feb 4, 2021 · Ok my be it’s not legacy but this function is only for gtk when you use imshow not in the main thread. zeros((512,512,3),np. VideoCapture(0) ret0, frame0 = cap0. Sep 27, 2021 · Defining a helper class for implementing multi-threading. – Dec 16, 2019 · One function is supposed to show local video and the other should show frames from my webcam. What I need to do is to stop and eventually restart the thread. imshow(window_name, image) Jul 20, 2014 · I want to display an image using opencv on Mac os X 13'. Traincascade with MultiThreading (TBB) -- Opencv-2. So It is initialized in main thread with cv::namedWindow ("display", 1), the running of another thread including cv::imshow ("display", image data) is after the initialization. GTK+, however, is not thread safe. 4 to 3. But when I am doing that my application is crashing , no imshow working . Therefore, I called the ThreadPoolExecutor Apr 19, 2016 · Finding features in several threads. waitKey() And this works fine. The code lacks any validation that imread succeeds, although I don't think that's the issue here. waitKey(25) Hope it'll help. avi', 'third. I could not find a way that these threads work on the same image or how I can merge the results into a new image. This is usually referred to as the “main thread”. # images is a list of openCV image object for img in images: cv2. Server. VideoCapture(0) Jul 24, 2012 · 2. The program I have is running on a single thread because of that the resulting video shown on the screen doesnt even look like a video, since there is a delay in detection process. First, we must define “performance” and how we intend to evaluate it. The threading is done like: I have a multi-threading application written in C++ with Qt5. __init__() self. You should only use GTK+ and GDK from the thread gtk_init() and gtk_main() were called on. Jan 18, 2022 · Hello. No code has changed from OCV 3. I posing my c code . 3 days ago · The function imshow displays an image in the specified window. Feb 16, 2014 · If you are running inside a Python console, do this: img = cv2. rowRange(0, rows). However, the opencv window is just blank and doesn't show the frames. VideoCapture. namedWindow ("image",0) img=cv2. Reference for Gdk-3. add a comment. I changed the pixel value as you suggested to 1 << 16 = 65535 and still see the issue. 4 and 3. Mar 14, 2021 · This doesn't answer the question, but it solves the problem: import cv2 import numpy as np from time import sleep import threading import time bitmap = np. and be careful with multithreading in general. Information will processed inside of that thread and copied to an array ("dataArray"). How to speed up this code implemented OpenCV. The imageCapture function is very straightforward and causes no trouble when running alone. The end goal is to utilize multiple processes to do this. jpg") cv2. Sometimes I am getting 20 fps( same as source) other times it drops to 3 fps ( means program loop stuck for a few seconds). It may will reduce your CPU usage. WND_PROP_VISIBLE) < 1: exit = True. namedWindow(window_name), the image is properly shown in a OpenCV-Window, caused by the line cv2. From the displayed Feb 1, 2016 · Hi , I am new on opencv development . 2. 5 and ubuntu 13. (Hardware is 4 cores. Only the first image displays properly. most of opencv's functionality is NOT THREADSAFE by design ! edit flag offensive delete link more freezes. I initialized 3 threads from threading class of Python. . private void button1_Click(object sender, EventArgs e) VideoCapture video = new VideoCapture("E I haven’t messed with multi threading, but according to the documentation, you have two options for starting a thread, and you haven’t done either. In this case I have stacked 4 images vertically. Problem with imshow in opencv 2. imshow("image",im) But I get this error: QObject::moveToThread: Current thread (0x11bdba0) is not the object's thread (0x15a18a0). the function has got opencv imread ( i checked using cvLoadimage but i got the same result) but programe can't complete and programe exit. May 25, 2022 · I'm trying to add a camera image showing component to an existing python program that shows multiple input in real time from various hardware devices. The displaying thread is just a consumer who fetches constantly the (window_name, image) pairs from the queue and all other image topic callback functions are just supplier who feeds The key to multi threading in OpenCV is to use only GPU functions which take a stream parameter. Those window decorations look like a Mac, and I recall seeing some questions about something similar. Otherwise, the image is scaled to fit the window. The function may scale the image, depending on its depth: Feb 25, 2023 · My goal is to cv::imshow("Live") and cv::imshow("ROI") on two different threads. read() is a blocking operation, our main program is stalled until the frame is read from the camera device and returned to our script. 5 Previously in OCV 2. import numpy as np. However, because I am new to opencv and multithreading, my implementation has caused my image processing functions to produce erroneous results. Mar 7, 2017 · I am getting different video streams from several cameras, which I would like to see in parallel using OpenCV imshow. What I want to do is to Aug 21, 2022 · you just need each thread to use a different name for the window in cv2. In order to do so, a call to the cv::imread function loads the image using the file path specified by the first argument. download(cpuImage, myStream); OpenCV cuda functions which don't take a stream may have buffer overwrite issues when accessed from multiple threads. You need to create a thread loop, initialise the windows in the thread (best just before the loop starts) and update your windows from within the loop. I am using Imshow() to display it. To display an image using opencv cv2 library, you can use cv2. start () — method to start the thread for reading next available frame. Oct 27, 2021 · Hello, My program is running in the thread it is just displaying the NumPy array from a special camera. VideoCapture(i) for i in names] To display the multiple images use subplot () plt. Jul 16, 2018 · The threads all work in the single core of your CPU but they halt in between their tasks and let the other thread take over. Dec 16, 2015 · Looking at the documentation for VideoCapture, it says "If there is a single camera connected, just pass 0. This copy process will be done while a class mutex is locked. 1 1. The function may scale the image, depending on its depth: Jan 6, 2018 · You can solve this by changing k=cv2. py and Worker. As in simultaneously modifying mat object. Dec 4, 2023 · In essence, cv2. Apr 22, 2021 · Given a base image, I would like to search it for multiple sub-images. Multi-threading camera stream to improve video processing performance Topics python opencv flask multi-threading camera live-streaming live-streaming-videos rtsp-stream threading-synchronization camera-streaming Jan 3, 2023 · Approach. from threading import Thread. Oct 26, 2022 · I cant get opencv to recognize mouse events with a simple program with no threads and classes, but I need to have two inputs open to the user, one window with a simple click twice to select a portion of the image, while at the same time responding to the command line text window for additional user input. I've been converting an OpenCV program from using cv::Mat to cv::UMat with the intention of increasing performance (which it does). Jun 20, 2017 · @AlexanderReynolds 0 means forever-- can't wait any longer that that. 04. Feb 24, 2016 · Sam Hartlebury. I read some of the previous Q/A and realize that highgui and multithreading don't go too well together, however, in this case I need to run it from a thread. png") cv2. org Gdk-3. But like I said, I want to declare and initialize the namedWindow outside of the callback function to prevent the above mentioned error, which may be an overflow caused by the recursive Oct 13, 2019 · counter. The ROI window is to display the frame that will be used to focus. s. jpg" from the OpenCV samples. Hi guys, I'm trying to build a multi-threading application. That might at least point to where the Apr 3, 2013 · removed the unnecessary read attempt code (which also removes the misleading thread re-read warnings after the last frame of a working video) used a video file that perhaps everyone with opencv has; removed the thread locking which didn't seem to matter to opencv at least on my system; moved a few other little things around Jan 17, 2018 · 0. I believe that putting the camera on a separate thread and having the Sep 13, 2021 · if cv2. その言語でのマルチスレッドの枠組みを確認する。. VIDEO_SOURCE = 0. Open up the extract. axarr[0]. #include &lt; Sep 30, 2020 · Stats. 画像処理・画像認識のプログラムを書くと、画像の処理・認識の時間に、次の画像を読み込んで Jul 30, 2021 · cv::imshow (“testWindow”, mTmpImage); // Never makes it to waitKey. 2) with ubuntu (18. avi', 'second. 以下の手順をふまえた。. 4 to 4. break. Then, another function called externally will copy that saved array ("dataArray") to a second array ("outArray") and return a pointer to the Mar 6, 2024 · This snippet demonstrates how to open multiple images in separate windows using OpenCV, which is useful when comparing images or when simultaneous visualization is required. The Live window is to display the frame captured by the Camera. height>0) in unknown function Jan 8, 2013 · The function imshow displays an image in the specified window. size(), image. call moveWindow ("first image", firstImageWidth + mySpacing , 0) Then, add these lines to prevent output windows from being forever active. 04 [closed] imshow namedWindow crash. 2) in my all threads except frame reading. time() try: while True: sleep(0. OpenCV imshow() – Display or Show Image. As a first step, we read the image "starry_night. 今回は、Python言語からC++言語での書き換えを勉強してみる。. It seems the issue occurs on copying the data. you can compile OpenCV with CUDA enabled. ) In the end, I was able to get about 10 frames/sec, with 260% load on a 4-core CPU. and create the boost thread and call the function inside that thread. imshow() doesn't work in threads but I'm not sure how to get around this? I would like in future to be able to run multiple cameras simultaneously and have multiple openv windows open showing the live streams. please anybody can help for that . Most of those questions about threading are in write context. 68 KB. May 17, 2015 · Im developing c++ application there i used boost, opencv. image) cv2. 3. However, I run into an error with the second NamedWindow command. imshow(window_name, cv_img). avi']; window_titles = ['first', 'second', 'third', 'fourth'] cap = [cv2. 4 I could create a namedWindow, start a new thread, and reference that namedWindow with imshow, waitKey, etc and, outside of that thread, call the mouse callback for that namedWindow. Thanks . clay. OpenCV Error: Assertion Failed (size. If the window was created with the cv::WINDOW_AUTOSIZE flag, the image is shown with its original size, however it is still limited by the screen resolution. Jun 27, 2022 · 0. 04 [closed] cv::mat in mfc. Sep 9, 2019 · If you need to review Python’s multiprocessing module, be sure to refer to the docs. May 17, 2021 · Im working on object detection from a live stream video using opencv python. Mar 18, 2020 · I'm trying to have a separate thread to display and process images coming from a webcam. C: set a ROI in the big image and copy your small image into it. Then you can write the code under GPU module. call imshow of opencv to display image. __init__ () — initialization method for starting video capture stream and creating a thread object. 04), and built with GTK support. Inside the cv2. from pyimagesearch. read() cv2. 4. imshow() function always takes two more functions to load and close the image. 0 Aug 1, 2019 · Closed for the following reason question is off-topic or not relevant by berak close date 2019-08-02 03:25:06. Here is the code: May 8, 2022 · to organize parallel captured frame processing pipeline. sleep (0. Because I need to display the feed in a cv2. Those operations cannot be in the main thread, since it's dedicated to other tasks. The syntax of imshow() function is given below. @LBerger, is race condition problem the reason I can't use multithread, in my case, there won't be 2 threads accessing window "display" at the same, after initialization in Jul 25, 2014 · 1) Read the images into a file, and put them in a C++ vector named imageQueue (a mutable array) 2) Create a number of threads. ny cd zs uw my jc ms ds sf px