How to write a open cam loop?

Question

Dekel Mashiach 2022-6-1

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1731840-how-to-write-a-open-cam-loop

回答： Pratyush Swain 2023-12-15

Hey; I'm trying to converte a code from reading a video to open cam ; hope someone can help me.

   videoName = 'tt1.mp4';
    videoReader = VideoReader(videoName);
    timeStamp = 0.06667;                   % time from the beginning of the video
    videoReader.CurrentTime = timeStamp;   % point to the chosen frame
    rgbImage = readFrame(videoReader); % read frame at timeStamp seconds
    figure
    imshow(rgbImage) % display frame

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Image Analyst 2022-6-1

WebCamDemo.zip

See attached sample code. Adapt as needed to do whatever algorithm you want.

Dekel Mashiach 2022-6-1

在 MATLAB Online 中打开

thanks. I need something like that but what can I write instead of Videoreader?

    
    cam = webcam('Microsoft® LifeCam HD-3000');
    preview(cam)
    % videoName = 'tt1.mp4';
    % videoReader = VideoReader(videoName);
    timeStamp = 0.06667;                   % time from the beginning of the video
    videoReader.CurrentTime = timeStamp;   % point to the chosen frame

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Answer 1

Pratyush Swain 2023-12-15

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https://ww2.mathworks.cn/matlabcentral/answers/1731840-how-to-write-a-open-cam-loop#answer_1372077

在 MATLAB Online 中打开

Hi Dekel,

I understand you are trying to convert the code from reading a video to opening a camera and reading from it.The "VideoReader" function in MATLAB is designed for reading video files, not for capturing live video streams from webcams.For the purpose of acquiring image from camera device, we have the leverage the "snapshot" function.

Please refer to the example implementation as follows:

% Check available webcams 
camList = webcamlist;
% Connect to the first webcam
cam = webcam(1);
% Configure camera settings (optional)
cam.Resolution = '640x480';
% Create a figure to show the captured images
hFigure = figure('Name', 'Webcam Stream', 'NumberTitle', 'off', 'CloseRequestFcn', @(src, event)setappdata(gcf, 'stopLoop', true));
% Set a flag for the loop to check
setappdata(hFigure, 'stopLoop', false);
% Create an axes object in the figure for displaying the image
hAxes = axes('Parent', hFigure);
% Loop to continuously capture images
while true
    % Check if the loop should stop (when the figure is closed)
    if getappdata(hFigure, 'stopLoop')
        break;
    end
    
    % Capture a single image
    img = snapshot(cam);
    
    % Display the captured image on the axes
    imshow(img, 'Parent', hAxes);
    
    % Pause for a brief moment to allow the display to update
    pause(0.1);
    
    % Allow other callbacks to process
    drawnow;
end
% Close the preview if it was started
closePreview(cam);
% Clear the webcam object when done
clear('cam');
% Delete the figure if it is still open
if isvalid(hFigure)
    delete(hFigure);
end

The above workflow will help to retreive images from the webcam or camera device and stream them continuosly over figure window. Please make sure to install all the support packages necessary to access mobile device sensors from MATLAB , install either MATLAB Support Package for Apple iOS Sensors or MATLAB Support Package for Android Sensors.

For more information on "snapshot" function, please refer to

1- https://www.mathworks.com/help/matlab/ref/mobilesensor.internal.camera.snapshot.html

2- https://www.mathworks.com/help/matlab/matlab_env/get-add-ons.html

Hope this helps.