appdesigner : error in a code when playing frames of a video with a slider

Question

Marina Llopis Segura 2023-4-6

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https://ww2.mathworks.cn/matlabcentral/answers/1942454-appdesigner-error-in-a-code-when-playing-frames-of-a-video-with-a-slider

评论： Marina Llopis Segura 2023-4-11

采纳的回答： Kevin Holly

Hello, I want to make a program that by moving a slider plays all the frames of a video.

I have made this code

here I have created a property

I would like the slider to change its length to the length of the video that I have already saved in a variable that I have called longitudvideo and I would like to know if someone can find the error that I have in the code because only some color points are reproduced and not the frames of the video.

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Marina Llopis Segura 2023-4-11

thank you very much, thanks to you I got it.

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Answer 1

Kevin Holly 2023-4-7

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1942454-appdesigner-error-in-a-code-when-playing-frames-of-a-video-with-a-slider#answer_1211549

在 MATLAB Online 中打开

videoplayer.mlapp

It looks like you are using imshow with a double.

imshow(app.AllFrames(:,:,:,idx),'Parent',app.video)

If you have an 8 bit image, you can convert the image from a double to an int8 as such:

uint8(app.AllFrames(:,:,:,idx))

imshow(uint8(app.AllFrames(:,:,:,idx)),'Parent',app.video)

You could create something as shown below with an if condition (app attached):

% Properties that correspond to app components
    properties (Access = public)
        UIFigure              matlab.ui.Figure
        tiempo                matlab.ui.control.NumericEditField
        tiempoEditFieldLabel  matlab.ui.control.Label
        Slider                matlab.ui.control.Slider
        SliderLabel           matlab.ui.control.Label
        seleccionvideoButton  matlab.ui.control.Button
        video                 matlab.ui.control.UIAxes
    end
    
    properties (Access = private)
        AllFrames % Description
        v
    end
    
    % Callbacks that handle component events
    methods (Access = private)
        % Button pushed function: seleccionvideoButton
        function seleccionvideoButtonPushed(app, event)
            tipos = {'*.mp4;*.avi;*webm;*.mov'};
            [file,path] = uigetfile(tipos);
            if isequal(file,0)
                disp('seleccion cancelada')
            else
                videopath = fullfile(path,file);
                app.v = VideoReader(videopath);
                numFrames = app.v.NumFrames;
                app.AllFrames = zeros(app.v.Height,app.v.Width,3,numFrames);
                for a = 1:numFrames
                    frame = read(app.v,a);
                    app.AllFrames(:,:,:,a) = frame;
                end
            end
        end
        % Value changing function: Slider
        function SliderValueChanging(app, event)
            changingValue = event.Value;
            idx = floor(changingValue);
            if app.v.BitsPerPixel == 24
                imshow(uint8(app.AllFrames(:,:,:,idx)),'Parent',app.video)
            end
            b = roundn(changingValue,-2);
            app.tiempo.Value = b;
        end
    end