Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

Check return value in python tutorial #13877

Merged
merged 1 commit into from
Feb 22, 2019
Merged

Check return value in python tutorial #13877

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Jump to
Jump to file
Failed to load files.
Diff view
Diff view
48 changes: 28 additions & 20 deletions doc/py_tutorials/py_gui/py_video_display/py_video_display.markdown
View file
Open in desktop
Expand Up @@ -25,23 +25,27 @@ import numpy as np
import cv2 as cv

cap = cv.VideoCapture(0)

while(True):
if not cap.isOpened():
print("Cannot open camera")
exit()
while True:
# Capture frame-by-frame
ret, frame = cap.read()

# if frame is read correctly ret is True
if not ret:
print("Can't receive frame (stream end?). Exiting ...")
break
# Our operations on the frame come here
gray = cv.cvtColor(frame, cv.COLOR_BGR2GRAY)

# Display the resulting frame
cv.imshow('frame',gray)
if cv.waitKey(1) & 0xFF == ord('q'):
cv.imshow('frame', gray)
if cv.waitKey(1) == ord('q'):
break

# When everything done, release the capture
cap.release()
cv.destroyAllWindows()
@endcode
cv.destroyAllWindows()@endcode
`cap.read()` returns a bool (`True`/`False`). If frame is read correctly, it will be `True`. So you can
check end of the video by checking this return value.

Expand Down Expand Up @@ -75,13 +79,17 @@ import cv2 as cv

cap = cv.VideoCapture('vtest.avi')

while(cap.isOpened()):
while cap.isOpened():
ret, frame = cap.read()

# if frame is read correctly ret is True
if not ret:
print("Can't receive frame (stream end?). Exiting ...")
break
gray = cv.cvtColor(frame, cv.COLOR_BGR2GRAY)

cv.imshow('frame',gray)
if cv.waitKey(1) & 0xFF == ord('q'):
cv.imshow('frame', gray)
if cv.waitKey(1) == ord('q'):
break

cap.release()
Expand Down Expand Up @@ -123,20 +131,20 @@ cap = cv.VideoCapture(0)

# Define the codec and create VideoWriter object
fourcc = cv.VideoWriter_fourcc(*'XVID')
out = cv.VideoWriter('output.avi',fourcc, 20.0, (640,480))
out = cv.VideoWriter('output.avi', fourcc, 20.0, (640, 480))

while(cap.isOpened()):
while cap.isOpened():
ret, frame = cap.read()
if ret==True:
frame = cv.flip(frame,0)
if not ret:
print("Can't receive frame (stream end?). Exiting ...")
break
frame = cv.flip(frame, 0)

# write the flipped frame
out.write(frame)
# write the flipped frame
out.write(frame)

cv.imshow('frame',frame)
if cv.waitKey(1) & 0xFF == ord('q'):
break
else:
cv.imshow('frame', frame)
if cv.waitKey(1) == ord('q'):
break

# Release everything if job is finished
Expand Down