capture a snapshot and saving it to a matrix variable

I am trying to use my webcam to record and take snapshots and be able to save it as a matrix variable. This is the best code I found online so far but I keep getting an error. Could someone help me iether with a better code that will work on app designer or how to fix this error?

% Button pushed function: OnButton

function OnButtonPushed(app, event)

clear all; clc; close all

cam = webcam('FaceTime HD Camera');

frame = snapshot(cam);

im = image(app.UIAxes, zeros(size(frame), 'uint8'));

axis(app.UIAxes,'image');

preview(cam,im);

pause;

Reference to a cleared variable app.

Error in Final/OnButtonPushed (line 19)

im = image(app.UIAxes, zeros(size(frame), 'uint8'));

Error using matlab.ui.control.internal.controller.ComponentController/executeUserCallback (line 309) Error while evaluating Button PrivateButtonPushedFcn.,

Answer 1

[Ameer Hamza]

Are you using it inside App designer? Remove the line

clear all; clc; close all

[Ana Guerrero Rosario]

Yes that worked, do you know how to code for the webcma to stop recording?

[Ameer Hamza]

You can delete() the webcam object.

delete(cam)

[Ana Guerrero Rosario]

Yes thank you! So I created another button that when pressed will record the snapshot from the camera. Do you know how to code for that button to save the frames of the snapshot to a matrix so that I can continue using that matrix for later analysis?

[Ameer Hamza]

You can create properties in your app to share the data between different callback functions (a property can be defined from toolbar in the code view). For example, define a property named 'cam', and then inside the callback function, use app.cam

app.cam = webcam('FaceTime HD Camera');

Using this, all of the callback functions will be able to use app.cam variable. Then you can use

img = snapshot(app.cam)

inside the callback function of the other button to get the image from the webcam. If you want to share the images with other callback functions, then define 'img' as a property too and directly modify it

app.img{end+1} = snapshot(app.cam);

[Ana Guerrero Rosario]

Also, do you know how to code for a lamp to turn a different color n when the button "on" (which turns on the webcam) is on, and then change to a different color when a button "off" (turns off the video) is pushed?

[Ameer Hamza]

You can use the "Enable" property of the lamp to turn it on and off. You can also use the "Color" property to change its color.

[Ana Guerrero Rosario]

Hey, I keep tyring to put a rectangle on the camera plot I have. I added a callback on the plot and put rectangle(app.UIAxes, 'Position', [25,25,50,50])

but nothing shows up when I run the code. Do you know how to fix this?