Getting A Single Image

At least four steps are necessary to capture a single image from a Balluff device. These steps are explained with the help of source examples from ImpactControlCenter.

Step 1: The Device Needs To Be Initialized

DMR_Init( &hDMR );
DMR_GetDevice( &hDevice, dmdsmSerial, "*", 0, '*' );
DMR_OpenDevice( hDevice, &hDriverInterface );

Step 2: Request The Acquisition Of An Image

DMR_ImageRequestSingle( hDriverInterface, 0, 0 );
\endif
 
A live acquisition (running inside a thread function) could be implemented as follows:
 
\code
//-----------------------------------------------------------------------------
HOBJ getProp( HDRV hDrv, TDMR_ListType lt, const char* pPropName, const char* pListName )
//-----------------------------------------------------------------------------
{
  TPROPHANDLING_ERROR objResult;
  TDMR_ERROR dmrResult;
  HOBJ hProp;
  HLIST hList;
 
  // First locate the setting list named 'Base', which is always present
  if( ( dmrResult = DMR_FindList( hDrv, pListName, lt, 0, &hList ) ) == DMR_NO_ERROR )
  {
    // Now try to locate the property
    if( ( objResult = OBJ_GetHandle( baseList, pPropName, & hProp ) ) != PROPHANDLING_NO_ERROR )
    {
      printf( "OBJ_GetHandle failed: %d Handle: %d\n", objResult, hProp );
    }
  }
  else
  {
    printf( "DMR_FindList failed: %d\n", dmrResult );
  }
  return hProp;
}
 
//-----------------------------------------------------------------------------
void threadFn( HDRV hDriverInterface )
//-----------------------------------------------------------------------------
{
  HOBJ hReqCnt, hPropFPS;
  ImageBuffer* pIB;
  int result = DMR_NO_ERROR;
  hReqCnt = getProp( hDriverInterface, dmltSystemSettings, "RequestCount", 0 );
  hPropFPS = getProp( hDriverInterface, dmltStatistics, "FramesPerSecond", 0 );
 
  // pre-fill the default capture queue
  while( ( result = DMR_ImageRequestSingle( hDriverInterface, 0, 0 ) ) == DMR_NO_ERROR );
  if( result != DEV_NO_FREE_REQUEST_AVAILABLE )
  {
    printf( "DMR_ImageRequestSingle: Unexpected error(code: %d(%s))\n", result, DMR_ErrorCodeToString( result ) );
  }
 
  while( !s_boTerminated )
  {
    result = DMR_ImageRequestWaitFor( hDriverInterface, 500, 0, &requestNr );
    if( result == DMR_NO_ERROR )
    {
      frameCount = frameCount + 1;
      if( ( frameCount % 100 ) == 0 )
      {
        OBJ_GetF( hPropFPS, &fps, 0 );
        printf( "frames per second: %.5f\n", fps );
      }
      if( ( result = DMR_GetImageRequestBuffer( hDriverInterface, requestNr, &pIB ) ) == DMR_NO_ERROR )
      {
        mvDispSetImage( pDisp, pIB->vpData, pIB->iWidth, pIB->iHeight, pIB->pChannels[0].iPixelPitch*8, pIB->pChannels[0].iLinePitch );
        mvDispUpdate( pDisp );
        DMR_ImageRequestUnlock( hDriverInterface, requestNr );
        DMR_ImageRequestSingle( hDriverInterface, 0, 0 );
      }
      else
      {
        printf( "DMR_GetImageRequestBuffer: ERROR! Code %d\n", result );
      }
    }
    else
    {
      printf( "DMR_ImageRequestWaitFor: ERROR! Code %d\n", result );
    }
  }
  DMR_ImageRequestReset( hDriverInterface, 0, 0 );
  DMR_ReleaseImageRequestBufferDesc( &pIB ) );
}

Note

Images supplied to the user are locked for the driver. So if the user does not unlock the images, a permanent acquisition won't be possible as sooner or later all available requests will have been processed by the driver and have been returned to the user.

See also

Step 4.

Step 3: Wait Until The Image Has Been Captured

DMR_ImageRequestWaitFor( hDriverInterface, 500, 0, &requestNr );

Step 4: Unlock The Image Buffer Once The Image Has Been Processed:

DMR_ImageRequestReset( hDriverInterface, 0, 0 ) );
DMR_ReleaseImageRequestBufferDesc( &pIB ) );

Note

ImpactControlCenter acquires images with the help of a capture thread. In order to avoid performance losses, the image buffer is locked during either the live or single image acquisition.

So after displaying the image the unlock is necessary!