Using VideoCapture With OpenCV Python

Reading frames from a pre-captured video

import numpy as np
import cv2

#access a video from your disk
#to use the GIF in this example, convert to avi!
cap = cv2.VideoCapture('eg_videoRead.avi')


#we are going to read 10 frames 
#we store the frames in a numpy structure
#then we'll generate a minimum projection of those frames

frameStack=[]
numFrames=10

for fr in range(numFrames):
    cap.set(cv2.CAP_PROP_POS_FRAMES,fr) #specifies which frame to read next
    frame=cap.read() #read the frame
    #gray = cv2.cvtColor(frame[1], cv2.COLOR_BGR2GRAY) #convert to gray scale
    frameStack.append(frame[1]) #add current frame to our frame Stack
    
minProjection=np.min(frameStack,axis=0) #find the minimum across frames
cv2.imshow("projection", minProjection) #show the result

Using VideoCapture With OpenCV Java

There is no imshow in the java, you need to write a method for this. This method is a Mat2bufferedImage. Takes mat object as parameter and returns image.

public static void main(String[] args) {
    Mat frame = new Mat();
    //0; default video device id
    VideoCapture camera = new VideoCapture(0);
    JFrame jframe = new JFrame("Title");
    jframe.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    JLabel vidpanel = new JLabel();
    jframe.setContentPane(vidpanel);
    jframe.setVisible(true);

    while (true) {
        if (camera.read(frame)) {

            ImageIcon image = new ImageIcon(Mat2bufferedImage(frame));
            vidpanel.setIcon(image);
            vidpanel.repaint();

        }
    }
}