MATLAB IMAGE ACQUISITION TOOLBOX 3 Guida Utente Scaricare il pdf (Pagina 199)

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101

Creating and Executing Callback Functions

Using a Text String to Specify Callback Functions

You can specify the callback function as a string. For example, this code

specif ies the callback function

mycallback as the value of the start event

callback property

StartFcn for the video input object vid.

vid.StartFcn = 'mycal lback';

In th is case, t h e callb ack is eval ua ted in the MATLAB wo rk s pa ce.

Using a Cell Array to Specify Callback Functions

You can specify the callback function as a text string inside a cell array.

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 = {'myca llback'};

To specify additional parameters, include them as additional elements in

the cell array.

time = datestr(now,0) ;

vid.StartFcn = {'mycal lback',time};

Thefirsttwoargumentspassedtothecallback function are still the video

inputobject(

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 = @mycal lback;

To spec

ify additional parameters, include the function handle and the

parame

ters as elements in the cell array.

time = datestr(now,0) ;

vid.StartFcn = {@mycal lback,time};

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