I'm writing a program in python using OpenCV which detects the edges (Canny Edge Detector) from the footage my webcam records. I'm also using two track-bars in order to control the threshold values (in order for to understand how these values change the output of this edge detector).
The code I wrote is the following:
import cv2
import numpy as np
def nothing(x):
pass
img = np.zeros((300,512,3), np.uint8)
cv2.namedWindow('cannyEdge')
cv2.createTrackbar("minVal", "cannyEdge", 0,100, nothing)
cv2.createTrackbar("maxVal", "cannyEdge", 100,200,nothing)
cap = cv2.VideoCapture(0)
while(True):
minVal = cv2.getTrackbarPos("minVal", "cannyEdge")
maxVal = cv2.getTrackbarPos("maxVal", "cannyEdge")
#capture frame by frame
ret, frame = cap.read()
cv2.imshow('frame', frame)
edge = cv2.Canny(frame,minVal,maxVal)
#display the resulting frame
cv2.imshow('frame', edge)
if cv2.waitKey(1) & 0xFF == ord('q'):
break
#When everything is done, release the capture
cap.release
cv2.destroyAllWindows()
This program is for educational purposes only as I'm currently learning to use OpenCV.
Every time I run the program above the code seems to be working just fine but I get the following Error:
GLib-GObject-CRITICAL **: g_object_unref: assertion 'G_IS_OBJECT (object)' failed
I've searched for the reason this error occurs but I haven't found anything helpful. My instinct tells me that my implementation for the trackbars is wrong and thus it's causing this error.
The tutorials I used are the following:
OpenCV tutorials - Canny Edge Detector
OpenCV tutorials - Trackbars
Does anybody know why this error occurs? Any help will be appreciated!
I am running Ubuntu 14.04, OpenCV 3.2.0 and Python 2.7.6
Try making the track bars and displaying the image in the same window and see if the error persists. I bet it shouldn't. Change: cv2.imshow('cannyEdge', edge)
Have you created another window named "frame"? If not, it looks like you should change 'frame' to 'cannyEdge':
cv2.imshow('cannyEdge', frame)
Related
What I'm trying to achieve is to crop my roi in the video frame into a variable and then further send it as a parameter..
Consider in face detection, and that x,y,x+w,y+h are the coordinates of the roi, which is the face and my aim is to crop that face and to show it.
The code below is just to explain my error and problem...
import cv2
cap=cv2.VideoCapture("D:\\Downloads\\video2.mp4")
#x,y,w,h, will change according the video i.e. where the face is detected.
#For the purpose of explaining, i took these values.
x=50
y=100
w=75
h=90
while(cap.isOpened()):
_,frame=cap.read()
crop_frame=frame[y:y+h,x:x+w]
cv2.imshow("Frame",frame)
cv2.imshow("crop_frame",frame)
cv2.destroyAllWindows()
cap.release()
But upon doing this, I get this error:
crop_frame=frame[y:y+h,x:x+w]
TypeError: 'NoneType' object is not subscriptable
This error wasn't there when i was working with images but on video inputs, i get this error.
Any solution to this problem or any alternative solution?
Basically you are slicing None when the video ends and no frame can be read: None[y:y+h,x:x+w]
You should use the retval to check if there is a frame to process, see the doc here: cv::VideoCapture::read.
So, try this code as experiment:
import cv2
cap=cv2.VideoCapture("video.mp4")
while(cap.isOpened()):
ret, frame=cap.read()
if ret:
cv2.imshow("Frame", frame)
else:
print('None frame:', frame)
break
cv2.destroyAllWindows()
cap.release()
There is no rendering because there is no time to do so, that's why you need to look at the next example.
Follows a simple script as example. These are the main points:
First, your loop is missing waytKey() function to allow the rendering, see the doc
here.
If you want your variable outside the loop, you must define
it outside the loop.
Also, you should choose which frame to crop.
You can also add HighGui (https://docs.opencv.org/4.1.0/d7/dfc/group__highgui.html) controls for selecting the frame, etc.
import cv2
cap=cv2.VideoCapture("video.mp4")
x=50
y=100
w=75
h=90
crop_frame = None
while(cap.isOpened()):
ret, frame = cap.read()
# if ret: to be added
cv2.imshow("Frame",frame)
keypressed = cv2.waitKey(10)
if keypressed == ord('q'):
break
if keypressed == ord('f'):
crop_frame = frame[y:y+h,x:x+w]
cv2.imshow("crop_frame", crop_frame)
cv2.destroyAllWindows()
cap.release()
cv2.imwrite('crop_frame.jpg', crop_frame)
You run and it shows the video.
Press 'F' and the current frame is cropped and presented in a new window.
Press 'Q': the loop exists and the cropped frame is saved as an image.
i tried to modify the code in darknet.py to do detections in live video feed coming from the webcam. Just imported open cv library and did a bit of modifications in the main function. It was previously detecting single images i.e before importing opencv. But now i get this error. Can anyone please help ..
Error:
(python:7913): Gtk-ERROR **: GTK+ 2.x symbols detected. Using GTK+ 2.x and GTK+ 3 in the same process is not supported
Trace/breakpoint trap (core dumped)
My main function looked like this :
if name == "main":
net = load_net("cfg/yolov3.cfg", "yolov3.weights", 0)
meta = load_meta("cfg/coco.data")
cap = cv2.VideoCapture(0)
while(True):
ret, frame = cap.read()
cv2.imshow('frame',frame)
cv2.imwrite('check.jpg',frame)
r = detect(net, meta, "check.jpg")
print r
if cv2.waitKey(1) & 0xFF == ord('q'):
break
cap.release()
I'm on lubuntu 16.04, using OpenCV 3.2.0, Python 2.7 and encountering this error after a brief moment of imshow() displaying a window with my camera stream.
This error occurs randomly - the stream can run fine for half a minute before this happens, or it can happen right at the start when I first run the script.
ASSERT: "false" in file qasciikey.cpp, line 495
Aborted (core dumped)
My code appended below:
import numpy as np
import cv2
redcross_cascade = cv2.CascadeClassifier('rcrosscascade.xml')
cap = cv2.VideoCapture(2)
cv2.namedWindow('Haar', cv2.WINDOW_NORMAL)
while 1:
ret, img = cap.read()
gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
redcross = redcross_cascade.detectMultiScale(gray, 50, 50)
for (x,y,w,h) in redcross:
cv2.rectangle(img,(x,y),(x+w,y+h),(255,255,0),2)
cv2.imshow('Haar',img)
key = cv2.waitKey(1) & 0xff
if key == 27:
break
cap.release()
cv2.destroyAllWindows()
Would appreciate any assistance on this matter, thank you!
EDIT: I have identified the trigger for this error - movement from my usb optical mouse. Disconnecting the mouse prevents the error from resurfacing but I've yet to find a reason for this occurrence.
I was receiving this error when I was running my python program (which used cv2) via an SSH terminal. When I ran the program from the machine itself, the error went away. I assume this is due to some X11 issue.
I was receiving this error before. Different webcam has different performance.
My method is to write the cv2.waitKey function after cv2.imshow function.
I have encountered the same issue. My app is similar to yours. None of the fixes suggested here have worked for me. I found that if I start single stepping in debug mode through the cap.read(), I can continue running a full speed and the problem will go away, although this is not a good fix.
This is the code when i execute it:
You can see the frame opens but doesnt show anything
I want to use a usb camera with a raspberry pi 3 model b v1.2 using opencv 3.3 and python 2.7.
I work with opencv in an virtual enviroment.
import numpy as np
import cv2
cap = cv2.VideoCapture(0)
while(True):
ret, frame = cap.read() #Capture frame-by-frame
#Our operations on the frame come here
#gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
#Display resulting frame
cv2.imshow('frame',frame)
cv2.waitKey(10)
#if cv2.waitKey(1) & 0xFF == ord('q'):
# break
#when everything done, release the capture
cap.release()
cv2.destroyAllWindows()
I just have no idea how to get around this error. I already searched the error and i am getting helpless, anyone having an idea?
EDIT: i am currently playing around with the code and i can get frames but most of the time the screen stays grey. I use # to show how the code looks now
Ok, it now opens a window and shows the output of the camera
Because of this code:
import sys
sys.path.append('/home/pi/.virtualenvs/cv/lib/python2.7/site-
packages/usr/local/lib/python2.7/site-packages')
and i also use sudo python program.py in the terminal
But this Error :"NameError: name 'CV_CAP_PROP_FRAME_HEIGHT' is not defined" still persists...
For my image processing algorithm I'm using python / OpenCV. The output of my algorithm shall be updated im the same window over and over again.
However sometimes the window freezes and doesn't update at all, but the algorithm is still running and updated the picture a multiple times in the meantime. The window turns dark gray on this Ubuntu machine.
Here is an excerpt of the involved code:
for i in range(0,1000):
img = loadNextImg()
procImg = processImg(img)
cv2.imshow("The result", procImg)
cv2.waitKey(1)
N.B.: processImg() takes about 1-2 s for its procedures. The line cv2.imshow(procImg) creates the window in first instance (i.e. there is no preceding invocation)
My suggestion is to use Matplotlib pyplot for displaying the image. I do it the following way.
import matplotlib.pyplot as plt
# load image using cv2....and do processing.
plt.imshow(cv2.cvtColor(image, cv2.BGR2RGB))
# as opencv loads in BGR format by default, we want to show it in RGB.
plt.show()
I know it does not solve the problem of cv2.imshow, but it solves our problem.
Increasing the wait time solves this issue. However in my opinion this is unnecessary time spent on sleeping (20 ms / frame), even though it's not much.
Changing
cv2.waitKey(1)
to
cv2.waitKey(20)
prevents the window from freezing in my case. The duration of this required waiting time may vary on different machines.
Just add cv2.destroyAllWindows() just after cv2.waitKey()
I have the very same issue and I noticed that the fps the window is updated is getting slower and slower until it freezes completely.
Increasing the waitKey(x) to something higher just extends the duration where the images are updated but when the time that cv2.imshow() needs to calculate exceeds the time from wait(Key) it just stops updating.
(Skip this complainment:)
I think the cv2.imshow() with waitKey() combination is a complete design error, why isn't imshow() just blocking until the UI is updated? That would make life so much easier without having to call waitKey() everytime...
P.S.: There is a possibility to start an own thread for opencv windows inside opencv:
import cv2
img = cv2.imread("image.jpg")
cv2.startWindowThread()
cv2.namedWindow("preview")
cv2.imshow("preview", img)
source: cv2.imshow command doesn't work properly in opencv-python
Well this doesn't work for me because I always get this errors when I run it:
(python3:1177): GLib-GObject-CRITICAL **: g_object_unref: assertion 'G_IS_OBJECT (object)' failed
Attempt to unlock mutex that was not locked
Aborted
Maybe you could try it and report if it is working for you?
Edit:
Okay I solved the problem for me by creating a separate script imshow.py:
import cv2
import os.path
while True:
if os.path.exists("image.pgm"):
image = cv2.imread("image.pgm")
if not image is None and len(image) > 0:
cv2.imshow("Frame", image)
cv2.waitKey(20)
And I am writing the image out in my other program with: cv2.imwrite("image.pgm", image)
And I am calling the script like this:
import subprocess
subprocess.Popen(["python3", "imshow.py"])
Although this is creating some dirty reads sometimes it is sufficient enough for me, a better solution would be to use pipes or queues between the two processes.
So what I think is going on here is that the window,(an element of the highGUI) which is still active after the first call to imshow, is waiting for some sort of response from your waitKey function, but is becoming inactive since the program is stuck calculating in either the processImg of loadNextImg functions. If you don't care about a slight waste of efficiency (i.e. you're not running on an embedded system where every operation counts), you should just destroy the window after waitKey, and recreate before imshow. Since the window no longer exists during the time you are processing and loading images, the highGUI wont get stuck waiting for a call from waitKey, and it won't become unresponsive.
If your window is going grey then it might be take more processing power. So try to resize image into smaller size image and execute. Sometimes times it freezes while running in ipython notebooks due to pressing any key while performing operation. I had personally executed your problem but I didn't get grey screen while doing it. I did executing directly using terminal. Code and steps are shown below.
import argparse
import cv2
import numpy as np
# construct the argument parser and parse the arguments
ap = argparse.ArgumentParser()
ap.add_argument("-i", "--image", required=True, help="Path to the image")
args = vars(ap.parse_args())
# load the image, grab its dimensions, and show it
image = cv2.imread(args["image"])
(h, w) = image.shape[:2]
cv2.imshow("Original", image)
cv2.waitKey(0)
for i in range(0,1000):
image = cv2.imread(args["image"])
cv2.imshow("The result",image);
cv2.waitKey(0)
Run it in terminal:
source activate env_name
python Filename.py --image Imagename.png
This will get to your result in one window only(updating each time) without freezing and if you want seperate image in every new window then add .format(i) as given below. But Remember to run in terminal only not in jupyter notebooks.
You can check using terminal commands in this video link
https://www.youtube.com/watch?v=8O-FW4Wm10s
for i in range(0,1000):
image = cv2.imread(args["image"])
cv2.imshow("The result{}".format(i),image);
cv2.waitKey(0)
This may help to get you 1000 images separately.
try:
import cv2
except:
print("You need to install Opencv \n Run this command \n pip install python-opencv")
exit()
print('Press q to quit frame')
def viewer(name,frame):
while True:
cv2.imshow(name,frame)
if cv2.waitKey(10) & 0xff ==ord('q'):
break
return
cv2.destroyWindow(name)
Save this program and from now onwards, import this and use the function viewer to display any frame/image and your display windows will not hang or crash.
Add the following two lines of code after cv2.imshow() function,
cv2.waitKey()
cv2.destroyAllWindows()
You can use while loop to take burst images without freezing. Here is an example for taking 10 images. You can also try to increase waitkey number and sleep time in while loop. This work for me.
key = cv2.waitKey(1)
webcam = cv2.VideoCapture(0)
sleep(1)
while True:
try:
check, frame = webcam.read()
cv2.imshow("Capturing", frame)
key = cv2.waitKey(1)
img_counter = 0
if key & 0xFF == ord('s'): #press s to take images
while img_counter < 10:
check, frame = webcam.read()
cv2.imshow("Capturing", frame)
key = cv2.waitKey(1)
path = 'F:/Projects/' #folder path to save burst images
img_name = "burst_{}.png".format(img_counter)
cv2.imwrite(os.path.join(path, img_name), img=frame)
print("Processing image...")
img_ = cv2.imread(img_name, cv2.IMREAD_ANYCOLOR) #save as RGB color format
print("{} written!".format(img_name))
img_counter += 1
sleep(0.2)
webcam.release()
cv2.destroyAllWindows()
break
elif key == ord('q'): #press q to quit without taking images
webcam.release()
cv2.destroyAllWindows()
break
except(KeyboardInterrupt):
print("Turning off camera.")
webcam.release()
print("Camera off.")
print("Program ended.")
cv2.destroyAllWindows()
break
This is an old thread but in case someone else encounters it, normally the issue happen when you update opencv/opencv-contrib versions with pip and still some of their dependencies are unmet (for example you might have numpy already installed so it wont reinstall it and this causes it to crash in the back).
Simply do
pip install opencv-python opencv-contrib-python --no-cache --force-reinstall
Version 4.5.2.52 is working fine on ubuntu 20.04 and 18.04 with python > 3.8