问题
I am creating GUI to play video files. The problem is that when I pause video, Play button cannot re-play that video, and I have to select video file again.
Note: Since I want to show video in the same tkinter window, I don't use OpenCV imshow command. Instead, I am using "window.after" method.
Following is my code:
I try to use "self.pause" variable to control pause status. When I click Pause button, this Boolean variable becomes True. However, I couldn't find suitable place to make it False when I click Play button again.
from tkinter import *
from tkinter import messagebox
from tkinter import filedialog
import PIL.Image, PIL.ImageTk
import cv2
class videoGUI:
def __init__(self, window, window_title):
self.window = window
self.window.title(window_title)
top_frame = Frame(self.window)
top_frame.pack(side=TOP, pady=5)
bottom_frame = Frame(self.window)
bottom_frame.pack(side=BOTTOM, pady=5)
self.pause = False # Parameter that controls pause button
self.canvas = Canvas(top_frame)
self.canvas.pack()
# Select Button
self.btn_select=Button(bottom_frame, text="Select video file", width=15, command=self.open_file)
self.btn_select.grid(row=0, column=0)
# Play Button
self.btn_play=Button(bottom_frame, text="Play", width=15, command=self.play_video)
self.btn_play.grid(row=0, column=1)
# Pause Button
self.btn_pause=Button(bottom_frame, text="Pause", width=15, command=self.pause_video)
self.btn_pause.grid(row=0, column=2)
self.delay = 15 # ms
self.window.mainloop()
def open_file(self):
self.pause = False
self.filename = filedialog.askopenfilename(title="Select file", filetypes=(("MP4 files", "*.mp4"),
("WMV files", "*.wmv"), ("AVI files", "*.avi")))
print(self.filename)
# Open the video file
self.cap = cv2.VideoCapture(self.filename)
self.width = self.cap.get(cv2.CAP_PROP_FRAME_WIDTH)
self.height = self.cap.get(cv2.CAP_PROP_FRAME_HEIGHT)
self.canvas.config(width = self.width, height = self.height)
def get_frame(self): # get only one frame
try:
if self.cap.isOpened():
ret, frame = self.cap.read()
return (ret, cv2.cvtColor(frame, cv2.COLOR_BGR2RGB))
except:
messagebox.showerror(title='Video file not found', message='Please select a video file.')
def play_video(self):
# Get a frame from the video source, and go to the next frame automatically
ret, frame = self.get_frame()
if ret:
self.photo = PIL.ImageTk.PhotoImage(image = PIL.Image.fromarray(frame))
self.canvas.create_image(0, 0, image = self.photo, anchor = NW)
if not self.pause:
self.window.after(self.delay, self.play_video)
def pause_video(self):
self.pause = True
# Release the video source when the object is destroyed
def __del__(self):
if self.cap.isOpened():
self.cap.release()
##### End Class #####
# Create a window and pass it to videoGUI Class
videoGUI(Tk(), "EnJapan")
If I write following code in "play_video" function:
self.pause = False
Pause button will not work. Because "window.after" method calls "play_video" function automatically and make the "self.pause" as False. Therefore, Pause button will have no effect.
回答1:
Question: Pause button will have no effect.
Reference:
Tkinter.Widget.after-method - after(delay_ms, callback=None, *args)
Registers an callback that is called after a given time.
Tkinter.Widget.after_cancel-method - after_cancel(id)
Cancels an callback.
To cancel the allready queued events for self.play_video change the following:
def play_video(self):
...
if self.pause:
self.window.after_cancel(self.after_id)
else:
self.after_id = self.window.after(self.delay, self.play_video)
回答2:
I would create another method for the play button callback. Something like this:
def play_start(self):
self.pause = False
self.play_video()
However, I would make sure you disable the play button if it's already playing. Otherwise, you could have multiple "instances" of play_video going if the play button is pressed multiple times.
An alternative is to combine your play and pause button, so it toggles the value of self.pause. Then you could have just one button with one callback function.
回答3:
simple In play_video(self) method
if self.pause == True: self.pause=False return
回答4:
from tkinter import *
from tkinter import messagebox
from tkinter import filedialog
import PIL.Image, PIL.ImageTk
import cv2
class videoGUI:
def __init__(self, window, window_title):
self.window = window
self.window.title(window_title)
top_frame = Frame(self.window)
top_frame.pack(side=TOP, pady=5)
bottom_frame = Frame(self.window)
bottom_frame.pack(side=BOTTOM, pady=5)
self.pause = False # Parameter that controls pause button
self.canvas = Canvas(top_frame)
self.canvas.pack()
# Select Button
self.btn_select=Button(bottom_frame, text="Select video file", width=15, command=self.open_file)
self.btn_select.grid(row=0, column=0)
# Play Button
self.btn_play=Button(bottom_frame, text="Play", width=15, command=self.play_video)
self.btn_play.grid(row=0, column=1)
# Pause Button
self.btn_pause=Button(bottom_frame, text="Pause", width=15, command=self.pause_video)
self.btn_pause.grid(row=0, column=2)
# Resume Button
self.btn_resume=Button(bottom_frame, text="resume", width=15, command=self.resume_video)
self.btn_resume.grid(row=0, column=3)
self.delay = 15 # ms
self.window.mainloop()
def open_file(self):
self.pause = False
self.filename = filedialog.askopenfilename(title="Select file", filetypes=(("MP4 files", "*.mp4"),
("WMV files", "*.wmv"), ("AVI files", "*.avi")))
print(self.filename)
# Open the video file
self.cap = cv2.VideoCapture(self.filename)
self.width = self.cap.get(cv2.CAP_PROP_FRAME_WIDTH)
self.height = self.cap.get(cv2.CAP_PROP_FRAME_HEIGHT)
self.canvas.config(width = self.width, height = self.height)
def get_frame(self): # get only one frame
try:
if self.cap.isOpened():
ret, frame = self.cap.read()
return (ret, cv2.cvtColor(frame, cv2.COLOR_BGR2RGB))
except:
messagebox.showerror(title='Video file not found', message='Please select a video file.')
def play_video(self):
# Get a frame from the video source, and go to the next frame automatically
ret, frame = self.get_frame()
if ret:
self.photo = PIL.ImageTk.PhotoImage(image = PIL.Image.fromarray(frame))
self.canvas.create_image(0, 0, image = self.photo, anchor = NW)
if not self.pause:
self.window.after(self.delay, self.play_video)
def pause_video(self):
self.pause = True
#Addition
def resume_video(self):
self.pause=False
self.play_video()
# Release the video source when the object is destroyed
def __del__(self):
if self.cap.isOpened():
self.cap.release()
##### End Class #####
# Create a window and pass it to videoGUI Class
videoGUI(Tk(), "EnJapan")
来源：https://stackoverflow.com/questions/54472997/video-player-by-python-tkinter-when-i-pause-video-i-cannot-re-play