How to store images in an array ?

I've already read similar topics here in the comunity, but it's not clear for me yet.

Image sizes are 480x720x3 uint8

I want to replicate the folowing code made in Python/OpenCV. For that I need to be able to store my images in an array. But no matter what I do, I dont seem to get it right.

• PYTHON

def get_background(file_path):
    cap = cv2.VideoCapture(file_path)
    % we will randomly select 50 frames for the calculating the median
    frame_indices = cap.get(cv2.CAP_PROP_FRAME_COUNT) * np.random.uniform(size=50)
    %  we will store the frames in array
    frames = []
    for idx in frame_indices:
        %  set the frame id to read that particular frame
        cap.set(cv2.CAP_PROP_POS_FRAMES, idx)
        ret, frame = cap.read()
        frames.append(frame) 
    %  calculate the median
    median_frame = np.median(frames, axis=0).astype(np.uint8)
    return median_frame

This code returns the background of a video, by selecting random 50 frames and calculating the median of those frames.

Is it possible to store images like this ?

• MATLAB

    randomframes = randi([1 numFrames],1,30);        % Generate 30 random numbers from the total number of frames.
    
    for n= 1:(30)                             % run through randomframes vector.
    frames(n) = read(vid, randomframes(n));   % store the image from a random frame in "frames(1....n)"
     end

Answer 1

[yanqi liu]

sir，please check the follow code to get some information

for more information,you can read the book 《计算机视觉与深度学习实战》，Thank you！

clc; clear all; close all;
vid = VideoReader('xylophone.mp4');
numFrames=vid.NumberOfFrames;
% Generate 30 random numbers from the total number of frames
randomframes = randi([1 numFrames],1,30);    
frames = [];
for n= 1:(30)                             
    % run through randomframes vector.
    % store the image from a random frame in "frames(1....n)"
    frames(:,:,:,n) = mat2gray(read(vid, randomframes(n)));   
end
figure; montage(frames, 'Size', [5 6], 'BackgroundColor', 'w', 'BorderSize', [3 3])

median_frame = median(frames,4);
figure; imshow(mat2gray(median_frame));

Answer 2

[Image Analyst]

You can store the images in a 3-D array. Something like (untested):

redImages = zeros(rows, columns, 50, 'uint8');
greenImages = zeros(rows, columns, 50, 'uint8');
blueImages = zeros(rows, columns, 50, 'uint8');
for k = 1 : 50
    rgbImage = getsnapshot(); % However you get it...
    [thisR, thisG, thisB] = imsplit(rgbImage);
    redImages(:, :, k) = thisR;
    greenImages(:, :, k) = thisG;
    blueImages(:, :, k) = thisB;
end
% Get medians for each z-column.
medRed = zeros(rows, columns, 'uint8');
medGreen = zeros(rows, columns, 'uint8');
medBlue = zeros(rows, columns, 'uint8');
for col = 1 : columns
    for row = 1 : rows
        medRed(row, col) = median(redImages(row, col, :));
        medGreen(row, col) = median(greenImages(row, col, :));
        medBlue(row, col) = median(blueImages(row, col, :));
    end
end