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Numpy Arrays

asked 2016-02-10 10:15:58 -0600

Nain gravatar image

I am using python bindings to convert a project ,initially made in C++ , in python. The following is the snapshot of some part of the code :

cv::Mat debugImage;
CvCapture* capture;
cv::Mat frame;
capture = cvCaptureFromCAM( -1 );
  if( capture )
      while( true ) 
        frame = cvQueryFrame( capture );
        // mirror it
        cv::flip(frame, frame, 1);

Here frame is defined as matrix which is then copied to the debugImage matrix inside the loop. But if I use numpy arrays declaration for frame and debugimage and then copy it using the copyto method of numpy, it throws error. Please help me to covert this code into python.

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answered 2016-02-10 10:39:27 -0600

berak gravatar image

updated 2016-02-10 10:46:06 -0600

aww, you're looking at outdated c-api code from pre 2010 (which is not using numpy arrays to store images or generic matrices)

take a close look at the python tutorials and, ofc, the sample codes

but here's the nutshell:

import cv2
import numpy as np

cam = cv2.VideoCapture(0)
while cam.isOpened():
   ok,img =
   if (not ok):
       continue # maybe you got an oldish webcam, that needs some 'warmup'
    # if you had a video **file** instead, you want to break here instead (reached last frame)
    # your img processing would go here ;)
    cv2.imshow("lalala", img)
    k = cv2.waitKey(10) & 0xff
    if k==27:
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This I know very well. Please tell me how to conver the debugImage matrix and the frame matrix into numpy arrays

Nain gravatar imageNain ( 2016-02-10 11:07:27 -0600 )edit

not sure, if i understand you correctly here: conver the debugImage matrix and the frame matrix

berak gravatar imageberak ( 2016-02-10 11:27:43 -0600 )edit

In the original code above, debugImage and frame are declared as Matrix . The frame is being used to capture the frames from the camera and then it copies the contents of frame matrix to the debugImage matrix. Now when I try to do the same in python by declaring debugImage matrix and frame as numpy arrays , python throws an error. Please tell me how to code this then.

Nain gravatar imageNain ( 2016-02-13 01:46:53 -0600 )edit

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Asked: 2016-02-10 10:15:58 -0600

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Last updated: Feb 10 '16