OpenCV in Python

Installation

Using Miniconda we’re installing the opencv-package for Python.

First follow the instructions in the Miniconda manual if you do not yet have a miniconda-environment in your home-directory.

Install the opencv-package:

# create python virtual environment
$ conda create -n opencv
$ conda activate opencv
# set 'conda-forge'-channel as default (first) channel
$ conda config --add channels conda-forge
# download and install packages from conda-forge channel
$ conda install libopencv opencv py-opencv

source: https://github.com/conda-forge/opencv-feedstock

Loading movies

Movie (5 seconds) is taken with iPhone and copied to computer (IMG_5915.MOV). In the example code below the image is read in with openCV, resized and converted to gray-scale. Finally the video is shown:

import cv2
import numpy as np

# Create a VideoCapture object and read from input file
# If the input is the camera, pass 0 instead of the video file name
cap = cv2.VideoCapture('IMG_5915.MOV')

# Check if camera opened successfully
if (cap.isOpened()== False):
    print("Error opening video stream or file")

width  = cap.get(cv2.CAP_PROP_FRAME_WIDTH)   # float
height = cap.get(cv2.CAP_PROP_FRAME_HEIGHT)  # float
fps = cap.get(cv2.CAP_PROP_FPS)
frameCount = cap.get(cv2.CAP_PROP_FRAME_COUNT)
print("size: %dx%d, fps: %.1f, frame count: %.1f, length: %.1f s"\
      %(int(width), int(height), fps, frameCount, frameCount/fps))

# Read until video is completed
while(cap.isOpened()):
    # Capture frame-by-frame
    ret, frame = cap.read()

    if ret == True:

        # Display the resulting frame
        cv2.imshow('Frame', gray)

        # Press Q on keyboard to  exit
        if cv2.waitKey(25) & 0xFF == ord('q'):
            break

    # Break the loop
    else:
        break

# When everything done, release the video capture object
cap.release()

# Closes all the frames
cv2.destroyAllWindows()

source: https://www.learnopencv.com/read-write-and-display-a-video-using-opencv-cpp-python/

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Last update: 2020-04-03