I'm working with OpenCV and trying to figure this out. When I want to read and show an image:
import cv2
img = cv2.imread('baboon.jpg', 0)
cv2.imshow('image', img)
cv2.waitKey(0)
cv2.destroyWindow('image')
I write this. But whenever the image display window pops up, I'm not able to close it and execute everything after
cv2.imshow('image', img)
cv2.waitKey(0)
cv2.destroyWindow('image')
because the window will not close unless I quit it.
For example, if I run this code
import cv2
img = cv2.imread('baboon.jpg', 0)
cv2.imshow('image', img)
cv2.waitKey(0)
cv2.destroyWindow('image')
#Nothing after this will get executed
print('Hello')
I get no output in my console, but the image window does pop up.
How can I fix this?
(I'm using Pycharm if that helps)
EDIT:
It seems that whenever I press any key the window closes and it works as intended (code after the comment is executed). Not sure why this is happening.
I believe the quit is acting as an interrupt, which quits the entire python program. This is different than pressing a key, which is incorporated into the logic of the actual program and continues to completion:
cv2.waitKey(0) # waits for any key to be pressed to continue the logic of the program
# this is what actually allows you to "display" an image without it immediately disappearing.
I believe you can click on anywhere in the pic and it would return to the code window
Related
I followed this program tutorial that captures the screen and puts it in a video file. The recording stops when the 'q' button is pressed. However, I didn't want to show the screen in a mini window and just write straight to the file. I am just calling the while loop shown in the tutorial except that I didn't include the part about showing the image to the 'Live' window. Now when I use:
while True:
img = pyautogui.screenshot()
frame = np.array(img)
frame = cv2.cvtColor(frame, cv2.COLOR_BGR2RGB)
out.write(np.array(frame))
# cv2.imshow('Live', frame)
if cv2.waitKey(1) == ord('q'):
print('done')
break
it won't detect my pressing q. What is going on here? When I press q the loop should stop right? I am just getting a 44 bit mp4 file as an end result from this. I think it might be because I didn't use imshow so waitkey won't do anything but I am not sure. Is there a way to get it to stop recording on a key press?
It's very likely that waitKey() doesn't do anything unless there's a window, since it's likely related to a window key event handler.
If you're on Windows, you could try msvcrt.kbhit(), which is a non-blocking call to request whether a key has been pressed on the console and could be read.
On other platforms, waiting for a keypress in a non-blocking manner might be non-trivial.
I think, you are right in assuming that since you didn't start the display(ie., cv2.imshow()) the cv2.watikey() doesn't work. Since your goal is to stop recording on key press I think you can follow this link's suggestion.
or try this pattern:
try:
while True:
break
#replace break with your code
except KeyboardInterrupt:
print("Press Ctrl-C to terminate while statement")
pass
I am using OpenCV in python and the aim of the code is to display one image after another in the same window without destroying it. For eg. i1.jpg is displayed and then in the same window left arrow is displayed after a pause of 5s.
In my case, i1.jpg is displayed and then the window is destroyed and then i2.jpg is displayed in another window.
Here is the code for the same -
t_screen_time = 5000
import numpy
import cv2
left_arrow = "left_arrow.jpg"
right_arrow = "right_arrow.jpg"
img = cv2.imread(left_arrow)
cv2.imshow('image',img)
cv2.waitKey(t_screen_time)
cv2.destroyAllWindows()
img = cv2.imread(right_arrow)
cv2.imshow('image',img)
cv2.waitKey(t_screen_time)
cv2.destroyAllWindows()
The argument in cv2.waitKey() is the time to wait for a keypress and not exactly the time the image is displayed for.
cv::imshow() or cv2.imshow() was not designed to be a complete GUI. It was designed to let you quickly debug and display images/videos.
You can achieve what you need using some form of sleep() in a thread or so. But this is harder to do in python. You could also just edit your code to
t_screen_time = 5000
import numpy
import cv2
left_arrow = r"first/image"
right_arrow = r"second/image"
img = cv2.imread(left_arrow)
cv2.imshow('image',img)
cv2.waitKey(t_screen_time)
img = cv2.imread(right_arrow)
cv2.imshow('image',img)
cv2.waitKey(t_screen_time)
cv2.destroyAllWindows()
by removing the cv2.destroyAllWindows() before displaying the second image. I've tested this code and it works, but if you're looking for more GUI functionality, use something like Qt.
I see it is possible to resize window with OpenCV, for example:
import cv2
img = cv2.imread('Test.jpg')
cv2.imshow('image',img)
cv2.namedWindow('image',cv2.WINDOW_NORMAL)
cv2.resizeWindow('image', 600,600)
cv2.waitKey(0)
cv2.destroyAllWindows()
But is it possible to minimize current window?
I think this is maybe cv2.setWindowProperty()this function for example here is fullscreen
cv2.namedWindow("window", cv2.WND_PROP_FULLSCREEN)
cv2.setWindowProperty("window",cv2.WND_PROP_FULLSCREEN,cv2.WINDOW_FULLSCREEN)
cv2.imshow("window", img)
Well, there is no function/method in openCV official documentation to minimize the window automatically. You can try different method with python to do the task. Such method can be found here: Is there a way to minimize a window in Windows 7 via Python 3?
Though i'm posting it here too for complete reference:
To minimize a window you need to know either the title of the window, or its window class. The window class is useful when the exact window title is not known. For example the following script shows two different ways to minimize the Microsoft Windows Notepad application assuming:
import ctypes
notepad_handle = ctypes.windll.user32.FindWindowW(None, "Untitled - Notepad")
ctypes.windll.user32.ShowWindow(notepad_handle, 6)
notepad_handle = ctypes.windll.user32.FindWindowW(u"Notepad", None)
ctypes.windll.user32.ShowWindow(notepad_handle, 6)
To determine the class name to use, you would need to use an tool such as Microsoft's Spy++. Obviously if Notepad was opened with a file, it would have a different title such as test.txt - Notepad. If this was the case, the first example would now fail to find the window, but the second example would still work.
If two copies of notepad were running, then only one would be closed. If all copies needed to be closed, you would need to enumerate all windows which requires more code.
The ShowWindow command can also be used to restore the Window.
Maybe this code will help you, I use it to detect mouse events to minimize the opencv GUI when I click it, obviously, you can create another more interesting application with this:
import cv2
import numpy as np
import win32gui,win32con
a = np.zeros((200,200,3),np.uint8)
def tactil_sec(event,x,y,flags,param):
if event == cv2.EVENT_LBUTTONDOWN:
cv2.imshow("LOL",a)
Minimize = win32gui.GetForegroundWindow()
win32gui.ShowWindow(Minimize, win32con.SW_MINIMIZE)
cv2.namedWindow('LOL')
cv2.setMouseCallback('LOL',tactil_sec)
while 1:
cv2.imshow("LOL",a)
if (cv2.waitKey(20) & 0xFF == 27):
break
cv2.destroyAllWindows()
I'm trying out SimpleCV and I'm noticing every time I click title bar, simplecv stops working to the pint that it crashes. Before crashing it says "pythonw.exe Stopped working." That happens if I edit my script and run it from the python idle. If I simply double click it, the image is displayed for 20secs and then just closes.
This is what I tried. Really simple.
from SimpleCV import Image
img = Image("carro.jpg")
img = img.scale(300,300)
img.show()
Just wondering if this could causes any kind of trouble while doing some image processing like subtracting colors and stuff like that.
Had the same problem and after searching found this: From http://help.simplecv.org/question/1118/why-imageshow-freezes/ it looks like it is caused by pyGame requiring a while loop to keep pumping events to the window.
The solution, as indicated at that post, and worked for me, was to use the quit() method on the window handle returned by show.
````
img = Image("carro.jpg")
img = img.scale(300,300)
win = img.show()
#wait for user input before closing
raw_input()
win.quit()
````
I'm using opencv 2.4.7 on ubuntu 12.04. I'm programming with python and I have a problem when i run this script:
import cv2
img = cv2.imread('347620923614738322_233985812.jpg')
cv2.namedWindow("window")
cv2.imshow("window", img)
cv2.waitKey(0)
The problem is that the script doesn't stop when I close the image. I searched information about waitKey and I found that using cv2.waitKey(0) is correct.
I don't understand, where is the problem?
I found that it works if i press the key whilst the window is in focus. If the command line is in focus then nothing happens
Adding a cv2.waitKey(1) after you destroy the window should work in this case.
cv2.imshow('imgae',img)
cv2.waitKey(0)
cv2.destroyAllWindows()
cv2.waitKey(1)
This code works for me from IDLE:
# -*- coding: utf-8 -*-
# Objectif : découvrir le fonctionnement d'opencv-python
# http://opencv-python-tutroals.readthedocs.org/en/latest/index.html
import numpy as np
import cv2
# Load an color image in grayscale
img = cv2.imread('Lena.tiff',0)
WINDOW_NAME = 'Image de Lena'
cv2.namedWindow(WINDOW_NAME, cv2.CV_WINDOW_AUTOSIZE)
cv2.startWindowThread()
# Display an image
cv2.imshow(WINDOW_NAME,img)
cv2.waitKey(0)
cv2.destroyAllWindows()
Hope this helps for future readers.
click on the image window(active) and then press and key, don't write in the terminal window.
Here a minimalistic code for best performance on all platforms:
import cv2
img = cv2.imread("image.jpg")
cv2.imshow("Window", img)
cv2.waitKey(0)
cv2.destroyAllWindows()
And now some observations:
When the user wants to close the window through the press of the 0 key, he/she has to make sure that the 0 key is pressed whilst the window is in focus. Because as stated above, if the terminal is in focus nothing happens and code execution stucks at the cv2.waitKey(0) until the 0 key is pressed properly whilst the window is in focus.
Pressing the 0 key whilst the window is in focus is the right way to close the window and make sure that, once the window is destroyed in line cv2.destroyAllWindows() and the program ends, the user can get back the control of the terminal.
If the window is exited by mouse click, the window will be destroyed yes, but the user will very much end up in the situation of not being able to get back the control of the terminal. In this kind of situation the user may want to shut down the unresponsive terminal and open a new one.
Try to execute the script directly from the Terminal works 100% for me but not from an IDE for example , i explain :
I'm using fedora 20 and got the same problem, copying the first example from official opencv python tutorial, i'm using :
Fedora 20 64bit
Spyder IDE for python
Python Version 2.7.5
Fedora 64 bit
OpenCV 2.4.7
Here is the code for test
import cv2
img = cv2.imread('/path/image1.jpeg',0)
cv2.imshow('Display',img)
cv2.waitKey(0)
cv2.destroyAllWindows()
When running this script using F5 from Spyder, it runs it using the embedded python terminal with this line :
runfile('/home/user/Workspace/test.py', wdir=r'/home/user/Workspace')
In this instance, cv2.waitKey(0) or cv2.waitKey(-1) are not working and windows remains opened after pressing keys with the code of the example
Trying to close the windows will result in a "Not Responding , Force to Quit" Alert
But when executing the script from Terminal , it works 100%
didn't found the problem origin , will update if i find it.
Solved in Spyder under Ubuntu by following [Run]->[Configuration per file]->[Execute in an external system terminal].
Well the use cv2.waitKeyEx(0).
It runs in the same way and waits for your response until you revoke it.
I hope it helps.
Nithesh varmma
cv2.waitKey(0) means that script is in infinity loop with 0 miliseconds wait after loop
.only specified key can stop it.
you did not specified end of app condition.
Try this code:
Using other keys for the waitKey() function of opencv
There is a problem with unix based system running opencv programs from python notebooks.
Check this alternate method My suggestion is to run code in python in terminal. You will not face any kind of problem
Copy the same code and save with filename.py
import cv2
input = cv2.imread('path_to_image.png')
cv2.imshow('Hello World', input)
cv2.waitKey(0)
cv2.destroyAllWindows()
then open specific directory and then open terminal
Steps:
Open Terminal
cd path/to/filename.py
source activate YOURPROFILE
python filename.py
This will solve problem
https://youtu.be/8O-FW4Wm10s
This will work even if you close the window using the cross button on the window.
import numpy as np
import cv2
img = cv2.imread('arvid.jpg', 0)
cv2.namedWindow('image', cv2.WINDOW_NORMAL)
cv2.imshow('image', img)
while True:
k = cv2.waitKey(30) & 0xFF
if k == 27: # wait for ESC key to exit
cv2.destroyAllWindows()
elif k == ord('s'): # wait for 's' key to save and exit
cv2.imwrite('arvid2.jpg', img)
cv2.destroyAllWindows()
if cv2.getWindowProperty("image", 0) == -1:
break
This problem occurs in some earlier version of opencv.
So you just need to update opencv to the latest version. Version 4.0.0.21 worked for me.
Use the command below.
update opencv to version 4.0.0.21.