Acquire an image from a live video while projecting on it a rectangle

Hi, I have the image acquisition toolbox and I've tried several ways to do this but I can't figure it out.

My goal is to use the getsnapshot function (idk if there is another way) manually when I place a checkerboard near from a rectangle that I have projected on the camera laptop preview (by using patch funtion e.g. to make the rectangle).

I've tried this by making a GUI or AppDesigner but my problem is that after executing getsnaphot I have to save the image on the Matlab's workspace but idk how to this.

This is an example of what I am trying to do:

But I only need to project the borders and not all the grid

I tried it with this code:

vid = videoinput('winvideo');

set(vid,'FramesPerTrigger',inf);
set(vid,'ReturnedColorspace','rgb');
vid.FrameGrabInterval = 2; %cada 5 frames cogemos uno nuevo

start(vid);

while (vid.FramesAcquired <= 200)
   
    data = getsnapshot(vid);
    
    imshow(data);
    
    hold on;
    axis ij;
    patch('Faces',face,'Vertices',vert,'FaceAlpha',0);
    hold off
    
end

stop(vid);
flushdata(vid);

delete(vid);
clear vid 

The rectangle projects well, and the effect of live video is working by taking and showing multiple frames by imshow.

However, the problem here is that in order to do this, I am constantly taking snapshots but I have to save only one (when the checkerboard is close enough to the projected rectangle and I decide to save it) by pushing a button from a GUI or AppDesigner e.g. (Idk if there is another possibility).

Any help would be appreciated,

Thanks

Answer 1

[Sid Singh]

Hi, you are using the patch command to draw the grid. There is a way to avoid Face colors by using

v = [0 0; 1 0; 1 1];
f = [1 2 3];
figure
patch('Faces',f,'Vertices',v,...
    'EdgeColor','green','FaceColor','none','LineWidth',2);

You can refer this documentation for more details under Polygon Edges Without Faces.

https://www.mathworks.com/help/matlab/ref/patch.html#d117e1022951