How do I actively control a webcam in app designer using a toggle switch?

Question

Ty Olmstead 2019-1-31

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/442454-how-do-i-actively-control-a-webcam-in-app-designer-using-a-toggle-switch

评论： Abdulrahman 2020-2-7

I have an application where I am using a stereo camera system that inputs one large image from two cameras into Matlab. I take a snapshot and then sparse the image into two images, crop, offset, display, etc using a subroutine ShowImages. I would like to be able to view the images live while I align the system that is collecting them. Currently I am using a while loop that is linked to a toggle switch. When the toggle switch changes the while loop breaks. Although the code seems to work, it is extremely slow. It can take 20 seconds after the switch is changed to off before the system responds. Is there a way to get the system to respond faster?

        % Value changed function: CamsLiveSwitch
        function CamsLiveSwitchValueChanged(app, event)
            while isequal(app.CamsLiveSwitch.Value,'On')  
                app.AquiringImagesLamp.Color = [0 1 0];
                % Display image and stretch to fill axes
                ShowImages(app) % This function manipulates the imagery for display
                if isequal(app.CamsLiveSwitch.Value,'Off') 
                    break;
                end
            end
            app.AquiringImagesLamp.Color = [1 0 0];

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Geoff Hayes 2019-1-31

Ty - I haven't used App Designer for GUIs but if you want to interrupt the "tight" while loop you could add a pause to it so that the change to the state of the toggle button is "captured". For example,

while isequal(app.CamsLiveSwitch.Value,'On')  
    app.AquiringImagesLamp.Color = [0 1 0];
    % Display image and stretch to fill axes
    ShowImages(app) % This function manipulates the imagery for display
    if isequal(app.CamsLiveSwitch.Value,'Off') 
        break;
    end
    pause(0.001);
end

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Answer 1

Kevin Chng 2019-2-22

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/442454-how-do-i-actively-control-a-webcam-in-app-designer-using-a-toggle-switch#answer_362183

The algorithm logic given by Geoff Hayes is right.

Code below is the code you may consider to put into the callback function of your 'toggle switch' in app designer.

 value = app.Switch.Value;
            if strcmp(value,'On')
            cam=webcam;
                while(strcmp(value,'On'))                
                img=snapshot(cam);
                imshow(img,'Parent',app.UIAxes);
                drawnow;
                value = app.Switch.Value;
                    if strcmp(value,'Off')
                        break;
                    end
                end
            end