程序未终止（tkinter openCV线程）

Question

我尝试构建一个GUI应用程序，从相机抓取帧并在Tkinter GUI中显示它们。Tkinter mainloop在主线程中执行，而gui的帧抓取和更新在单独的线程中进行。

下面的代码作为一个视频流被抓取并正确显示在我的gui窗口中。但是，当我通过单击“x”来调用on_close（）方法来关闭gui时，gui将关闭，但程序不会完全终止。最后一次CLI输出将为“Mainloop stopped！”，但该计划并没有像我预期的那样终止。因此，即使我通过stop事件退出threads run（）方法中的while循环，我还是怀疑额外的线程会继续运行。

这是我的代码：

import threading    
import cv2
import tkinter
from tkinter import ttk
from PIL import Image
from PIL import ImageTk

import camera


class mainThread(threading.Thread):

    def __init__(self, gui):
        threading.Thread.__init__(self)
        self.stop_event = threading.Event()
        self.gui = gui

    def stop(self):
        print("T: Stop method called...")
        self.stop_event.set()

    def run(self):
        print("Connecting to camera...")
        cam = camera.Camera(resolution=(1280, 960), exposure=-3, bit_depth=12)
        cam.connect(device_id=0)

        while (not self.stop_event.is_set()):
            print("running..., stop event = " + str(self.stop_event.is_set()))
            # retrieve frame and frame time
            frame, _, _ = cam.get_frame()

            # display frame
            self.gui.updater(frame)

            # wait for displaying image
            cv2.waitKey(1)


class gui(object):

    def __init__(self, root):

        self.root = root

        # create and start thread running the main loop
        self.main_thread = mainThread(self)
        self.main_thread.start()

        # bind on close callback that executes on close of the main window
        self.root.protocol("WM_DELETE_WINDOW", self.on_close)

        # change window title
        self.root.title("MCT Laser Welding Quality Control")

        # set min size of root window and make window non resizable
        self.root.minsize(600, 400)
        self.root.resizable(False, False)

        # configure grid layout
        self.root.rowconfigure(0, weight=1)
        self.root.rowconfigure(1, weight=1)
        self.root.columnconfigure(0, weight=1)

        # create image panel
        self.image_panel = None

    def on_close(self):
        self.main_thread.stop()
        self.root.destroy()

    def updater(self, image):

        # TODO: resize frame first

        # convert image to tkinter image format
        image = Image.fromarray(image)
        image = ImageTk.PhotoImage(image)

        # if the panel does not exist, create and pack it
        if self.image_panel is None:

            # show the image in the panel
            self.image_panel = ttk.Label(self.root, image=image)
            self.image_panel.image = image  # keep reference

            # pack object into grid
            self.image_panel.grid(row=0, column=0)

        # just update the image on the panel
        else:
            self.image_panel.configure(image=image)
            self.image_panel.image = image  # keep reference

    def run(self):
        self.root.mainloop()


if __name__ == "__main__":

    # create a main window
    root = tkinter.Tk()

    # set style
    style = ttk.Style()
    style.theme_use("vista")

    # create gui instance
    user_interface = gui(root)

    # run the user interface
    root.mainloop()

    print("Mainloop stopped!")

编辑：我发现，这行

image = ImageTk.PhotoImage(image)

防止线程停止，如上所述。当我删除这一行并简单地用一个递增的数字更新标签文本时，当我关闭gui窗口时，一切都像例外一样工作，线程终止。任何想法，为什么ImageTk.PhotoImage（）导致线程不能正确终止？

Answer 1

您需要加入线程以等待它关闭。

def stop(self):
    print("T: Stop method called...")
    self.stop_event.set()
    self.join()

此外，您可能需要关闭摄像头的开放连接。

while (not self.stop_event.is_set()):
    ...
cam.close() # not sure about exact API here