Develop Reference

Python VideoCapture(0) my camera bad work

This my codes :
import numpy as np
import cv2
cap = cv2.VideoCapture(0)
while(True):
# Capture frame-by-frame
ret, frame = cap.read()
# Our operations on the frame come here
gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
# Display the resulting frame
cv2.imshow('frame',gray)
if cv2.waitKey(1) & 0xFF == ord('q'):
break
# When everything done, release the capture
cap.release()
cv2.destroyAllWindows()
I write the code like this and try to open my camera, but the camera image looks like the screenshot.
Stop working screen shot
Any idea ? What is the reason?

It's indentation problem.
Try this code:
import numpy as np
import cv2
cap = cv2.VideoCapture(0)
while(True):
# Capture frame-by-frame
ret, frame = cap.read()
# Our operations on the frame come here
gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
# Display the resulting frame
cv2.imshow('frame',gray)
if cv2.waitKey(1) & 0xFF == ord('q'):
break
# When everything done, release the capture
cap.release()
cv2.destroyAllWindows()
Provide proper indentation so the program works fine.
Press "q" to stop the program.

I can't see the videocapture

i am trying to learn some image processing using openCV and i wrote a basic code but the "frame" windows won't show.I've tried installing on a separate computer but i get the same problem.
import cv2
cap = cv2.VideoCapture(0);
while (True):
ret, frame = cap.read()
gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
cv2.imshow('frame', gray)
if cv2.waitKey(1) & 0xFF == ord('q'):
break
cap.release()
cv2.destroyAllWindows()

Based on the code you added your if statement is outside the while loop and therefore can never be checked. It should have thrown a different error however if that was the case. Your camera might be detected but not working. Try using it like a traditional webcam on another program like camera or photobooth to help troubleshoot the issue.
import cv2
cap = cv2.VideoCapture(0);
while (True):
ret, frame = cap.read()
gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
cv2.imshow('frame', gray)
if cv2.waitKey(1) & 0xFF == ord('q'):
break
cap.release()
cv2.destroyAllWindows()

Processing frame every second in opencv python

Here is the code for reading video file from webcam using opencv website. I just want to process the frame every second.
import numpy as np
import cv2
cap = cv2.VideoCapture(0)
while(True):
# Capture frame-by-frame
ret, frame = cap.read()
# Our operations on the frame come here
gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
# Display the resulting frame
cv2.imshow('frame',gray)
if cv2.waitKey(1) & 0xFF == ord('q'):
break
# When everything done, release the capture
cap.release()
cv2.destroyAllWindows()
How should I modify the code:

You should just make your process wait for one second before each read:
import numpy as np
import cv2
import time
cap = cv2.VideoCapture(0)
while(True):
# Capture frame-by-frame
start_time = time.time()
ret, frame = cap.read()
# Our operations on the frame come here
gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
# Display the resulting frame
cv2.imshow('frame',gray)
if cv2.waitKey(1) & 0xFF == ord('q'):
break
time.sleep(1.0 - time.time() + start_time) # Sleep for 1 second minus elapsed time
# When everything done, release the capture
cap.release()
cv2.destroyAllWindows()

Play video Basic

im new to python openCV,found this code from openCV page;
import cv2
cap = cv2.VideoCapture('Megamind.avi')
while (cap.isOpened()):
ret, frame = cap.read()
gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
cv2.imshow('MMR3', gray)
if cv2.waitkey(25) & 0xFF == ord('q'):
break
cap.release()
cv2.destroyAllWindows()*
Tried to run it but it gives error which after done some digging up, i replaced this line:
"cap = cv2.VideoCapture('Megamind.avi')" with this line:
"cap = cv2.VideoCapture('Megamind.avi', cv2.CAP_FFMPEG)"
The program run without error but the video windows("MMR3") was not displayed.
**Im using python 2.7.13 with opencv3 running on MacOs Sierra.
**Megamind.avi is available in the same folder where the code is

your cv2.imshow has to be in the whille loop. If your cv2.imshow() is outside while loop than it will only display the last frame of you video. Change you code to below code
import cv2
cap = cv2.VideoCapture('Megamind.avi')
while (cap.isOpened()):
ret, frame = cap.read()
gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
cv2.imshow('MMR3', gray)
if cv2.waitkey(25) & 0xFF == ord('q'):
break
cap.release()
cv2.destroyAllWindows()

error with cv2.destroyAllWindws() on ubuntu 14.04

I'm programing in python and opencv on Ubuntu but the cv2.destoyAllWindows() doesn't seem to work,as in this example:
import numpy as np
import cv2
cap = cv2.VideoCapture(0)
while(True):
# Capture frame-by-frame
ret, frame = cap.read()
# Our operations on the frame come here
gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
# Display the resulting frame
cv2.imshow('frame',gray)
if cv2.waitKey(1) & 0xFF == ord('q'):
break
# When everything done, release the capture
cap.release()
cv2.destroyAllWindows()
when i press 'q' the program end but the window remain on the screen how ever on windows i didn't face such thing
any help I will be thankful