MATLAB IMAGE ACQUISITION TOOLBOX - RELEASE NOTES Guide de l'utilisateur télécharger pdf (Page 241)

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Creating and Executing Callback Functions

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vid.StartFcn = {'mycallback'};

To specify additional parameters, include them as additional elements in the cell array.

time = datestr(now,0);

vid.StartFcn = {'mycallback',time};

The first two arguments passed to the callback function are still the video input

object (obj) and the event structure (event). Additional arguments follow these two

arguments.

Using Function Handles to Specify Callback Functions

You can specify the callback function as a function handle.

For example, this code specifies the callback function mycallback as the value of the

start event callback property StartFcn for the video input object vid.

vid.StartFcn = @mycallback;

To specify additional parameters, include the function handle and the parameters as

elements in the cell array.

time = datestr(now,0);

vid.StartFcn = {@mycallback,time};

If you are executing a local callback function from within a MATLAB file, you must

specify the callback as a function handle.

Specifying a Toolbox Function as a Callback

In addition to specifying callback functions of your own creation, you can also specify the

start, stop, or trigger toolbox functions as callbacks. For example, this code sets the

value of the stop event callback to Image Acquisition Toolbox start function.

vid.StopFcn = @start;

Disabling Callbacks

If an error occurs in the execution of the callback function, the toolbox disables the

callback and displays a message similar to the following.

start(vid)

??? Error using ==> frames_cb

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MATLAB IMAGE ACQUISITION TOOLBOX - RELEASE NOTES Guide de l'utilisateur Page 241

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