cv2 ndarray convert to list then backward to ndarray cannot display correctly
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1
I need to transmit my video stream via JSON format, so I try to convert ndarray which read from cv2 to list first, and then backward to ndarray again to read it. Here is my code in python.
video = cv2.VideoCapture(video_file)
while(video.isOpened()):
success, frame = video.read()
data = frame.tolist()
image = np.asarray(data)
cv2.imshow('frame', image)
if cv2.waitKey(1) & 0xFF == ord('q'):
break
video.release()
However, I just got a image with all black, not the original video screen. Why and how to correct it? Thank you.
python opencv numpy-ndarray
asked Nov 22 '18 at 1:52
Jay JJay J
2614
|
show 1 more comment
1
I need to transmit my video stream via JSON format, so I try to convert ndarray which read from cv2 to list first, and then backward to ndarray again to read it. Here is my code in python.
video = cv2.VideoCapture(video_file)
while(video.isOpened()):
success, frame = video.read()
data = frame.tolist()
image = np.asarray(data)
cv2.imshow('frame', image)
if cv2.waitKey(1) & 0xFF == ord('q'):
break
video.release()
However, I just got a image with all black, not the original video screen. Why and how to correct it? Thank you.
python opencv numpy-ndarray
asked Nov 22 '18 at 1:52
Jay JJay J
2614
1
Tryimage = np.asarray(data, dtype=np.uint8), my guess is you're converting fromuint8toint64andimshowis interpreting the data differently.
– jodag
Nov 22 '18 at 1:56
Thanks,it works. Can you give my some explain why this happen?
– Jay J
Nov 22 '18 at 1:59
Got it, thanks.
– Jay J
Nov 22 '18 at 1:59
1
Sure,frame.tolist()is converting fromnp.uint8to the default pythoninttype. When you convert back, numpy is interpreting that as anint64unless explicitly told not to.
– jodag
Nov 22 '18 at 2:00
No point in this transition ---frameis already a numpy array. Casting it to a list and then back to an array doesn't do anything.
– Alexander Reynolds
Nov 22 '18 at 2:00
|
show 1 more comment
1
1
1
I need to transmit my video stream via JSON format, so I try to convert ndarray which read from cv2 to list first, and then backward to ndarray again to read it. Here is my code in python.
video = cv2.VideoCapture(video_file)
while(video.isOpened()):
success, frame = video.read()
data = frame.tolist()
image = np.asarray(data)
cv2.imshow('frame', image)
if cv2.waitKey(1) & 0xFF == ord('q'):
break
video.release()
However, I just got a image with all black, not the original video screen. Why and how to correct it? Thank you.
python opencv numpy-ndarray
asked Nov 22 '18 at 1:52
Jay JJay J
2614
I need to transmit my video stream via JSON format, so I try to convert ndarray which read from cv2 to list first, and then backward to ndarray again to read it. Here is my code in python.
video = cv2.VideoCapture(video_file)
while(video.isOpened()):
success, frame = video.read()
data = frame.tolist()
image = np.asarray(data)
cv2.imshow('frame', image)
if cv2.waitKey(1) & 0xFF == ord('q'):
break
video.release()
However, I just got a image with all black, not the original video screen. Why and how to correct it? Thank you.
python opencv numpy-ndarray
python opencv numpy-ndarray
asked Nov 22 '18 at 1:52
Jay JJay J
2614
asked Nov 22 '18 at 1:52
Jay JJay J
2614
asked Nov 22 '18 at 1:52
Jay JJay J
2614
asked Nov 22 '18 at 1:52
Jay JJay J
2614
asked Nov 22 '18 at 1:52
Jay JJay J
2614
2614
1
Tryimage = np.asarray(data, dtype=np.uint8), my guess is you're converting fromuint8toint64andimshowis interpreting the data differently.
– jodag
Nov 22 '18 at 1:56
Thanks,it works. Can you give my some explain why this happen?
– Jay J
Nov 22 '18 at 1:59
Got it, thanks.
– Jay J
Nov 22 '18 at 1:59
1
Sure,frame.tolist()is converting fromnp.uint8to the default pythoninttype. When you convert back, numpy is interpreting that as anint64unless explicitly told not to.
– jodag
Nov 22 '18 at 2:00
No point in this transition ---frameis already a numpy array. Casting it to a list and then back to an array doesn't do anything.
– Alexander Reynolds
Nov 22 '18 at 2:00
|
show 1 more comment
1
Tryimage = np.asarray(data, dtype=np.uint8), my guess is you're converting fromuint8toint64andimshowis interpreting the data differently.
– jodag
Nov 22 '18 at 1:56
Thanks,it works. Can you give my some explain why this happen?
– Jay J
Nov 22 '18 at 1:59
Got it, thanks.
– Jay J
Nov 22 '18 at 1:59
1
Sure,frame.tolist()is converting fromnp.uint8to the default pythoninttype. When you convert back, numpy is interpreting that as anint64unless explicitly told not to.
– jodag
Nov 22 '18 at 2:00
No point in this transition ---frameis already a numpy array. Casting it to a list and then back to an array doesn't do anything.
– Alexander Reynolds
Nov 22 '18 at 2:00
1
1
Try
image = np.asarray(data, dtype=np.uint8), my guess is you're converting from uint8 to int64 and imshow is interpreting the data differently.– jodag
Nov 22 '18 at 1:56
Try
image = np.asarray(data, dtype=np.uint8), my guess is you're converting from uint8 to int64 and imshow is interpreting the data differently.– jodag
Nov 22 '18 at 1:56
Thanks,it works. Can you give my some explain why this happen?
– Jay J
Nov 22 '18 at 1:59
Thanks,it works. Can you give my some explain why this happen?
– Jay J
Nov 22 '18 at 1:59
Got it, thanks.
– Jay J
Nov 22 '18 at 1:59
Got it, thanks.
– Jay J
Nov 22 '18 at 1:59
1
1
Sure,
frame.tolist() is converting from np.uint8 to the default python int type. When you convert back, numpy is interpreting that as an int64 unless explicitly told not to.– jodag
Nov 22 '18 at 2:00
Sure,
frame.tolist() is converting from np.uint8 to the default python int type. When you convert back, numpy is interpreting that as an int64 unless explicitly told not to.– jodag
Nov 22 '18 at 2:00
No point in this transition ---
frame is already a numpy array. Casting it to a list and then back to an array doesn't do anything.– Alexander Reynolds
Nov 22 '18 at 2:00
No point in this transition ---
frame is already a numpy array. Casting it to a list and then back to an array doesn't do anything.– Alexander Reynolds
Nov 22 '18 at 2:00
|
show 1 more comment
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1
Try
image = np.asarray(data, dtype=np.uint8), my guess is you're converting fromuint8toint64andimshowis interpreting the data differently.– jodag
Nov 22 '18 at 1:56
Thanks,it works. Can you give my some explain why this happen?
– Jay J
Nov 22 '18 at 1:59
Got it, thanks.
– Jay J
Nov 22 '18 at 1:59
1
Sure,
frame.tolist()is converting fromnp.uint8to the default pythoninttype. When you convert back, numpy is interpreting that as anint64unless explicitly told not to.– jodag
Nov 22 '18 at 2:00
No point in this transition ---
frameis already a numpy array. Casting it to a list and then back to an array doesn't do anything.– Alexander Reynolds
Nov 22 '18 at 2:00