ContinuousCapture.win32.cpp

The ContinuousCapture.win32 program is a simple example for a continuous acquisition.

Note

This example will work on Windows® only. When a C++11 or higher capable compiler is available have a look a the ContinuousCapture.cpp example instead, which will run on any platform and uses much more sophisticated methods for capturing data!

Program location

The source file ContinuousCapture.win32.cpp can be found under:

%INSTALLDIR%\apps\ContinuousCapture\

Note

If you have installed the package without example applications, this file will not be available.

ContinuousCapture example:

1. Opens a Balluff device.
2. Snaps images continuously.

Console Output

[0]: BF000306 (mvBlueFOX-202C, Family: mvBlueFOX, interface layout: DeviceSpecific)

Please enter the number in front of the listed device followed by [ENTER] to open it: 0
Using device number 0.
Press [ENTER] to end the application
Initialising the device. This might take some time...
Info from BF000306: FramesPerSecond: 28.655660, ErrorCount: 0, CaptureTime_s: 0.104195
Info from BF000306: FramesPerSecond: 28.655636, ErrorCount: 0, CaptureTime_s: 0.104017
Info from BF000306: FramesPerSecond: 28.655659, ErrorCount: 0, CaptureTime_s: 0.104153
Info from BF000306: FramesPerSecond: 28.655636, ErrorCount: 0, CaptureTime_s: 0.104072
Info from BF000306: FramesPerSecond: 28.655660, ErrorCount: 0, CaptureTime_s: 0.104234

How it works

The continuous acquisition is similar to the single capture. The only major difference is, that this sample will continuously request images from the device. This is done without the need of a separate thread here but instead the keyboard is checked for input after every image captured. This is not the most elegant approach but the most portable and simple in this scenario.

However the general stuff (selection of a device etc.) is similar to the SingleCapture.cpp source example.

First of all the user is prompted to select the device he wants to use for this sample:

DeviceManager devMgr;
Device* pDev = getDeviceFromUserInput( devMgr );

The function getDeviceFromUserInput() is included via

#include <apps/Common/exampleHelper.h>

Then after the device has been initialised successfully image requests will constantly be sent to the drivers request queue and the application waits for the results:

// Pre-fill the capture queue with ALL buffers currently available. In case the acquisition engine is operated
// manually, buffers can only be queued when they have been queued before the acquisition engine is started as well.
// Even though there can be more than 1, for this sample we will work with the default capture queue
int requestResult = DMR_NO_ERROR;
int requestCount = 0;
 
if( boSingleShotMode )
{
  fi.imageRequestSingle();
  ++requestCount;
}
else
{
  while( ( requestResult = fi.imageRequestSingle() ) == DMR_NO_ERROR )
  {
    ++requestCount;
  }
}
 
if( requestResult != DEV_NO_FREE_REQUEST_AVAILABLE )
{
  cout << "Last result: " << requestResult << "(" << ImpactAcquireException::getErrorCodeAsString( requestResult ) << "), ";
}
cout << requestCount << " buffers requested";
 
if( ss.requestCount.hasMaxValue() )
{
  cout << ", max request count: " << ss.requestCount.getMaxValue();
}
cout << endl;
cout << "Press <<ENTER>> to end the application!!" << endl;
 
manuallyStartAcquisitionIfNeeded( pDev, fi );
// run thread loop
const Request* pRequest = 0;
const unsigned int timeout_ms = 8000;   // USB 1.1 on an embedded system needs a large timeout for the first image
int requestNr = -1;
bool boError = false;
while( !boError )
{
  // wait for results from the default capture queue
  requestNr = fi.imageRequestWaitFor( timeout_ms );
  if( fi.isRequestNrValid( requestNr ) )
  {
    pRequest = fi.getRequest( requestNr );
    if( pRequest->isOK() )
    {
      // process data
    }
    else
    {
      cout << "*** Error: request not OK, result: " << pRequest->requestResult << endl;
      boError = true;
    }
 
    // this image has been displayed thus the buffer is no longer needed...
    fi.imageRequestUnlock( requestNr );
    // send a new image request into the capture queue
    fi.imageRequestSingle();
  }
  else
  {
    // If the error code is -2119(DEV_WAIT_FOR_REQUEST_FAILED), the documentation will provide
    // additional information under TDMR_ERROR in the interface reference
    cout << "imageRequestWaitFor failed (" << requestNr << ", " << ImpactAcquireException::getErrorCodeAsString( requestNr ) << ")"
         << ", timeout value too small?" << endl;
    boError = true;
  }
 
  if( waitForInput( 0, STDOUT_FILENO ) != 0 )
  {
    cout << " == " << __FUNCTION__ << " finished by user - " << endl;
    break;
  }
}

With the request number returned by mvIMPACT::acquire::FunctionInterface::imageRequestWaitFor you can gain access the image buffer:

int requestNr = fi.imageRequestWaitFor( timeout_ms );
pRequest = fi.isRequestNrValid( requestNr ) ? fi.getRequest( requestNr ) : 0;

The image attached to the request can then be processed and/or displayed if the request does not report an error.

When the image is no longer needed you have to unlock the image buffer as otherwise the driver will refuse to use it again. This makes sure, that no image, that is still used by the user will be overwritten by the device:

pRequest->unlock();

Source code

//
// @description: Example applications for Impact Acquire
// @copyright: Copyright (C) 2005 - 2024 Balluff GmbH
// @authors: APIs and drivers development team at Balluff GmbH
// @initial date: 2005-03-15
//
// Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"),
// to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense,
// and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice (including the next paragraph) shall be included in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,i
// WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//
 
#ifdef _MSC_VER // is Microsoft compiler?
#   if _MSC_VER < 1300  // is 'old' VC 6 compiler?
#       pragma warning( disable : 4786 ) // 'identifier was truncated to '255' characters in the debug information'
#   endif // #if _MSC_VER < 1300
#endif // #ifdef _MSC_VER
#include <windows.h>
#include <process.h>
#include <iostream>
#include <apps/Common/exampleHelper.h>
#include <mvIMPACT_CPP/mvIMPACT_acquire.h>
#include <mvDisplay/Include/mvIMPACT_acquire_display.h>
 
using namespace mvIMPACT::acquire;
using namespace mvIMPACT::acquire::display;
using namespace std;
 
static bool s_boTerminated = false;
 
//=============================================================================
//================= Data type definitions =====================================
//=============================================================================
//-----------------------------------------------------------------------------
struct ThreadParameter
//-----------------------------------------------------------------------------
{
    Device*             pDev;
    ImageDisplayWindow  displayWindow;
    ThreadParameter( Device* p, const string& windowTitle ) : pDev( p ), displayWindow( windowTitle ) {}
};
 
//-----------------------------------------------------------------------------
unsigned int __stdcall liveThread( void* pData )
//-----------------------------------------------------------------------------
{
    ThreadParameter* pThreadParameter = reinterpret_cast<ThreadParameter*>( pData );
    cout << "Initialising the device. This might take some time..." << endl;
    try
    {
        pThreadParameter->pDev->open();
    }
    catch( const ImpactAcquireException& e )
    {
        // this e.g. might happen if the same device is already opened in another process...
        cout << "An error occurred while opening the device " << pThreadParameter->pDev->serial.read()
             << "(error code: " << e.getErrorCodeAsString() << ")." << endl
             << "Press [ENTER] to end the application..." << endl;
        cin.get();
        return 0;
    }
 
    ImageDisplay& display = pThreadParameter->displayWindow.GetImageDisplay();
    // establish access to the statistic properties
    Statistics statistics( pThreadParameter->pDev );
    // create an interface to the device found
    mvIMPACT::acquire::FunctionInterface fi( pThreadParameter->pDev );
 
    // Send all requests to the capture queue. There can be more than 1 queue for some devices, but for this sample
    // we will work with the default capture queue. If a device supports more than one capture or result
    // queue, this will be stated in the manual. If nothing is mentioned about it, the device supports one
    // queue only. This loop will send all requests currently available to the driver. To modify the number of requests
    // use the property mvIMPACT::acquire::SystemSettings::requestCount at runtime (note that some devices will
    // only allow to modify this parameter while NOT streaming data!) or the property
    // mvIMPACT::acquire::Device::defaultRequestCount BEFORE opening the device.
    TDMR_ERROR result = DMR_NO_ERROR;
    while( ( result = static_cast<TDMR_ERROR>( fi.imageRequestSingle() ) ) == DMR_NO_ERROR ) {};
    if( result != DEV_NO_FREE_REQUEST_AVAILABLE )
    {
        cout << "'FunctionInterface.imageRequestSingle' returned with an unexpected result: " << result
             << "(" << mvIMPACT::acquire::ImpactAcquireException::getErrorCodeAsString( result ) << ")" << endl;
    }
 
    manuallyStartAcquisitionIfNeeded( pThreadParameter->pDev, fi );
    // run thread loop
    mvIMPACT::acquire::Request* pRequest = 0;
    // we always have to keep at least 2 images as the displayWindow module might want to repaint the image, thus we
    // can free it unless we have a assigned the displayWindow to a new buffer.
    mvIMPACT::acquire::Request* pPreviousRequest = 0;
    const unsigned int timeout_ms = 500;
    unsigned int cnt = 0;
    while( !s_boTerminated )
    {
        // wait for results from the default capture queue
        int requestNr = fi.imageRequestWaitFor( timeout_ms );
        pRequest = fi.isRequestNrValid( requestNr ) ? fi.getRequest( requestNr ) : 0;
        if( pRequest )
        {
            if( pRequest->isOK() )
            {
                ++cnt;
                // here we can display some statistical information every 100th image
                if( cnt % 100 == 0 )
                {
                    cout << "Info from " << pThreadParameter->pDev->serial.read()
                         << ": " << statistics.framesPerSecond.name() << ": " << statistics.framesPerSecond.readS()
                         << ", " << statistics.errorCount.name() << ": " << statistics.errorCount.readS()
                         << ", " << statistics.captureTime_s.name() << ": " << statistics.captureTime_s.readS() << endl;
                }
                display.SetImage( pRequest );
                display.Update();
            }
            else
            {
                cout << "Error: " << pRequest->requestResult.readS() << endl;
            }
            if( pPreviousRequest )
            {
                // this image has been displayed thus the buffer is no longer needed...
                pPreviousRequest->unlock();
            }
            pPreviousRequest = pRequest;
            // send a new image request into the capture queue
            fi.imageRequestSingle();
        }
        //else
        //{
        // Please note that slow systems or interface technologies in combination with high resolution sensors
        // might need more time to transmit an image than the timeout value which has been passed to imageRequestWaitFor().
        // If this is the case simply wait multiple times OR increase the timeout(not recommended as usually not necessary
        // and potentially makes the capture thread less responsive) and rebuild this application.
        // Once the device is configured for triggered image acquisition and the timeout elapsed before
        // the device has been triggered this might happen as well.
        // The return code would be -2119(DEV_WAIT_FOR_REQUEST_FAILED) in that case, the documentation will provide
        // additional information under TDMR_ERROR in the interface reference.
        // If waiting with an infinite timeout(-1) it will be necessary to call 'imageRequestReset' from another thread
        // to force 'imageRequestWaitFor' to return when no data is coming from the device/can be captured.
        // cout << "imageRequestWaitFor failed (" << requestNr << ", " << ImpactAcquireException::getErrorCodeAsString( requestNr ) << ")"
        //   << ", timeout value too small?" << endl;
        //}
    }
    manuallyStopAcquisitionIfNeeded( pThreadParameter->pDev, fi );
 
    // stop the displayWindow from showing freed memory
    display.RemoveImage();
    // In this sample all the next lines are redundant as the device driver will be
    // closed now, but in a real world application a thread like this might be started
    // several times an then it becomes crucial to clean up correctly.
 
    // free the last potentially locked request
    if( pRequest )
    {
        pRequest->unlock();
    }
    // clear all queues
    fi.imageRequestReset( 0, 0 );
    return 0;
}
 
//-----------------------------------------------------------------------------
int main( void )
//-----------------------------------------------------------------------------
{
    DeviceManager devMgr;
    Device* pDev = getDeviceFromUserInput( devMgr );
    if( !pDev )
    {
        cout << "Unable to continue! Press [ENTER] to end the application" << endl;
        cin.get();
        return 1;
    }
 
    // start the execution of the 'live' thread.
    cout << "Press [ENTER] to end the application" << endl;
    unsigned int dwThreadID;
    string windowTitle( "mvIMPACT_acquire sample, Device " + pDev->serial.read() );
    // initialise displayWindow window
    // IMPORTANT: It's NOT safe to create multiple displayWindow windows in multiple threads!!!
    ThreadParameter threadParam( pDev, windowTitle );
    HANDLE hThread = ( HANDLE )_beginthreadex( 0, 0, liveThread, ( LPVOID )( &threadParam ), 0, &dwThreadID );
    cin.get();
    s_boTerminated = true;
    WaitForSingleObject( hThread, INFINITE );
    CloseHandle( hThread );
    return 0;
}