configuring callback properties -凯发k8网页登录

this example explains how callback functions work and shows how to use them.

callback functions are executed when an associated event occurs. to configure a callback to execute for a particular event, configure one of the video input object's callback properties:

errorfcn
framesacquiredfcn
startfcn
stopfcn
timerfcn
triggerfcn

this tutorial uses a callback function that displays the n'th frame, where n is provided as an input argument to the callback function.

select a device to use for acquisition and configure it to acquire data upon executing a manual trigger.

% access an image acquisition device.
vidobj = videoinput('winvideo', 1);
% acquire an infinite number of frames when manually triggered.
triggerconfig(vidobj, 'manual');
vidobj.framespertrigger = inf;

configure the video input object to execute a callback function when the acquisition is stopped.

% specify the n'th frame the callback function will display.
framenumber = 3;
% have the callback function executed when the acquisition ends.
vidobj.stopfcn = {'util_showframe', framenumber};
% initiate the acquisition.
start(vidobj)

upon triggering the image acquisition device, a tennis ball is dropped within the camera's view.

% trigger the object for logging and acquire data for a few seconds.
trigger(vidobj)
pause(5);

when the acquisition is stopped, it will cause the callback function to execute and display the n'th frame.

% stop the acquisition.
stop(vidobj)

once the video input object is no longer needed, delete it and clear it from the workspace.

delete(vidobj)
clear vidobj

configuring callback properties -凯发k8网页登录

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