Problems faced during implementation of cv2.imshow()

Question

I have been working on opencv lately. Installed it on my Ubuntu 16.04. I think it has a few problems. Whenever I try to run the function

cv2.imshow('frame',frame)

it poses this error

OpenCV Error: Unspecified error (The function is not implemented. 
Rebuild the library with Windows, GTK+ 2.x or Carbon support. 
If you are on Ubuntu or Debian, install libgtk2.0-dev and pkg-config, then re-run cmake or configure script) in cvShowImage, file /tmp/build/80754af9/opencv_1512687413662/work/modules/highgui/src/window.cpp, line 611
Traceback (most recent call last): 
     File "hands.py", line 12, in <module>
     cv2.imshow('frame',frame)
     cv2.error: /tmp/build/80754af9/opencv_1512687413662/work/modules/highgui/src/window.
cpp:611: error: (-2) The function is not implemented. Rebuild the library with Windows, GTK+ 2.x or Carbon support. 
    If you are on Ubuntu or Debian, install libgtk2.0-dev and pkg-config, then re-run cmake or configure script in function cvShowImage

The code I tried to run is

import numpy as numpy
import cv2
import matplotlib.pyplot as plt

cap = cv2.VideoCapture(0)
bg = cv2.bgsegm.createBackgroundSubtractorMOG()

while True:
    ret,frame = cap.read()
    vid = bg.apply(frame)

    cv2.imshow('frame',frame)
    cv2.imshow('vid',vid)
    key = cv2.waitKey(0) & 0xff
    if key == 27:
        break

cap.release()
cap.destroyAllWindows()

I tried to google every possible thing and did everything that's possible but still aren't able to solve the issue.

I also tried using

matplotlib.pyplot.imshow('frame',frame) 
matplotlib.pyplot.show()

instead of

cv2.imshow('frame',frame)

but this gives the error

TypeError: unhashable type: 'numpy.ndarray'

to show the video captured from my webcam. It either shows just a image and an error at cv2.waitkey() instead of the video or this error. Is there any method to solve this error? or to implement cv2 GUI features?

Please read and understand [mcve]. It is unclear what code you are running to obtain the error. How are we supposed to help here? — ImportanceOfBeingErnest, Dec 17 '17 at 15:38
Sorry about the incompleteness in my question, I have posted a piece of my code . Can you help me out with it? — Darshan, Dec 18 '17 at 17:30

score 0 · Answer 1 · answered Dec 18 '17 at 17:41

0

Seems like you have a problem with your cv2 installation. I cannot help with that, but I would recommend reinstalling and making sure the correct version for your system (matching OS, bit depth and python version) is used.

As a workaround you may indeed use matplotlib to show the image. A minimal example would be

import cv2
import matplotlib.pyplot as plt

cap = cv2.VideoCapture(0)

plt.ion()
fig, ax = plt.subplots()
ret,frame = cap.read()
im = ax.imshow(frame)

while True:
    ret,frame = cap.read()
    im.set_data(frame)
    plt.pause(0.5)

plt.ioff()
plt.show()

Also see update frame in matplotlib with live camera preview

answered Dec 18 '17 at 17:41

ImportanceOfBeingErnest

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Thanks for the answer but I am getting this error. `Image data cannot be converted to float` – Darshan Dec 20 '17 at 07:04
The last line is not enough, one needs to know the full error traceback. – ImportanceOfBeingErnest Dec 20 '17 at 09:22
`matplotlib/__init__.py in inner(ax, *args, **kwargs) 1715 warnings.warn(msg % (label_namer, func.__name__), 1716 RuntimeWarning, stacklevel=2) -> 1717 return func(ax, *args, **kwargs) matplotlib/axes/_axes.py in imshow(self, X, cmap, norm, aspect, interpolation, alpha, vmin, vmax, origin, extent, shape, filternorm, filterrad, imlim, resample, url, **kwargs) 5125 resample=resample, **kwargs) -> 5127 im.set_data(X)` – Darshan Dec 20 '17 at 10:12
`matplotlib/image.py in set_data(self, A) 605 if (self._A.dtype != np.uint8 and 606 not np.can_cast(self._A.dtype, float, "same_kind")): --> 607 raise TypeError("Image data cannot be converted to float")` --The complete error in cuts. – Darshan Dec 20 '17 at 10:16
It seems that VideoCapture does not return a valid image. Are you sure that there is some video stream to capture at address 0? – ImportanceOfBeingErnest Dec 20 '17 at 10:23
cv2.VideoCapture(0) is supposed to open my webcam and output the video captured. – Darshan Dec 20 '17 at 11:33
Yes, it is supposed to do that. And if it successfully does it, `frame` should be an image, which can be shown via `imshow`. (This is also what happens when I run the code.) That is why my suspicion is that something goes wrong when opening the videostream, such that it does not return a valid image. – ImportanceOfBeingErnest Dec 20 '17 at 12:02
I have done so much fixing the bug and I think I should erase everything out of my ubuntu and re install from the beginning . Can you please suggest something for it? – Darshan Dec 25 '17 at 12:45

Problems faced during implementation of cv2.imshow()

1 Answers1