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Reference manual

CvCam

Contents

INTRODUCTION .........................................................................................................................3

COMMON USAGE.......................................................................................................................3

HOWTO:........................................................................................................................................5

B

EGIN WORK WITH CVCAM

...........................................................................................................5

S

ELECT A CAMERA

G

ET THE POINTER TO LAST FRAME

................................................................................................6

P

LAY AN AVI FILE AND PROCESS IT

’

S FRAMES IF NEEDED

..............................................................7

W

...........................................................................7

W

F

INISH WORKING WITH CVCAM

CVCAM REFERENCE ................................................................................................................9

CVCAM

CVCAM

ROPERTIES

I

NTERFACE

.................................................................................................14

Introduction

CvCam is a universal cross-platform module for processing video stream from digital

video cameras. It is implemented as a dynamic link library (DLL) for Windows and as a shared

object library (so) for linux systems and provides a simple and convenient Application

Programming Interface (API) for reading and controlling video stream, processing its frames and

rendering the results. CvCam is distributed as a part of Intel’s OpenCV project under the same

license and uses some functionality of the Open Source Computer Vision Library.

#include “cvcam.h”

void callback(IplImage* image);

int main()

{

int ncams = cvcamGetCamerascount( );//returns the number of available cameras in the

//system

cvcamSetProperty(0, CVCAM_PROP_ENABLE, &cvcamone); //Selects the 1-st found

//camera

cvcamSetProperty(0, CVCAM_PROP_RENDER, &cvcamone) //We’ll render stream

//from this source

//process every frame

cvcamInit( );

cvcamStart( );

//Your app is working

cvcamStop( );

cvcamExit( );

return 0;

}

void callback(IplImage* image)//Draws blue horizontal lines across the image

{

{

for(j=(image1->widthStep)*i; j<(image1->widthStep)*(i+1);

j+=image1->nChannels)

{

image1->imageData[j] = (char)255;

image1->imageData[j+1] = 0;

image1->imageData[j+2] = 0;

}

number of available cameras at the system. On Linux it’s also important to call it before your

initialize the X window system as it prepares X to work with linux threads. Your can also call

XInitThreads( )

at the beginning of your app instead.

The next step is to choose a camera and set it up.

cvcamSetProperty( int camera, char* property,

void* arg)

can do this for you. See CvCam Properties Interface for complete list of properties

and arguments. The first argument for this function is the number of the camera for which the

property is set, the second is a property’s name and the third is a pointer to some data, which

actual type depends on the property. In the example above we selected a camera and told CvCam

to render it into the window we specified.

Next step is calling

cvcamStart( )

stream continues until

cvcamStop( )

And the last is

cvcamExit( )

–Frees all resources used by CvCam.

Howto:

Begin work with cvcam

Call

cvcamGetCamerasCount()

. This not only returns the number of cameras in the system,

but also prepares cvcam. Under linux be sure to do this call before initializing X, or to call

/*Pops up a camera(s) selection dialog

Return value - number of cameras selected (0,1 or 2);

Argument: an array of selected cameras numbers

NULL if none selected. Should be released with free() when not needed.

if NULL passed, not used.

*/

CVCAM_API int cvcamSelectCamera(int** out);

FunctionThatSelectsCamera()

{

free(out);

return;

}

Note: if you don’t need selected cameras numbers, simply call

cvcamSelectCamera(NULL)

Note2: Linux version of cvcam currently has no implementation of

cvcamSelectCamera