[osg-users] Saving Screenshot

[Danny Lesnik]

Hi,

I'm playing with OSG activeX example and trying to make screenshot of current scene, but I get black screenshot.

the Viewer initiation is the following:

Code:

_traits = new osg::GraphicsContext::Traits;
osg::ref_ptr<osg::Referenced> windata = new osgViewer::GraphicsWindowWin32::WindowData( GetSafeHwnd() );
_traits->x = 0;
_traits->y = 0;
_traits->width = rect.right - rect.left;
_traits->height = rect.bottom - rect.top;
_traits->windowDecoration = false;
_traits->doubleBuffer = true;
_traits->sharedContext = 0;
_traits->setInheritedWindowPixelFormat = true;
_traits->inheritedWindowData = windata;
_gc = osg::GraphicsContext::createGraphicsContext( _traits.get() );
_gc->setClearColor( osg::Vec4f(0.2f, 0.2f, 0.6f, 1.0f) );
_gc->setClearMask( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );

// Create camera
osg::ref_ptr<osg::Camera> camera = new osg::Camera;
camera->setGraphicsContext(_gc);
camera->setViewport( new osg::Viewport(_traits->x, _traits->y, _traits->width, _traits->height) );
camera->setProjectionMatrixAsPerspective( 30.0f, (double)_traits->width/(double)_traits->height, 1.0f, 10000.0f );
camera->setClearMask( GL_DEPTH_BUFFER_BIT );

// Create viewer
_viewer = new osgViewer::Viewer;
_viewer->setThreadingModel( osgViewer::Viewer::SingleThreaded );
_viewer->setCamera( camera.get() );
_viewer->setCameraManipulator( new osgGA::TrackballManipulator );

The part of the code which grabs screenshot is the following:

Code:

osgViewer::ScreenCaptureHandler* scrn = new osgViewer::ScreenCaptureHandler();
osgViewer::ScreenCaptureHandler::WriteToFile* captureOper = new osgViewer::ScreenCaptureHandler::WriteToFile(tmpStr.m_szBuffer, "png");
scrn->setCaptureOperation(captureOper);
scrn->captureNextFrame(*_viewer);
_viewer->frame();

I think I need to take screenshot from GraphicContext instead of viewer, but I have no idea how to do it.

Can you please help?

Thank you!

Cheers,
Danny

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[Danny Lesnik]

Hi,

Does anybody have any clue? how to solve this problem?

Thank you!

Cheers,
Danny

------------------
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http://forum.openscenegraph.org/viewtopic.php?p=22922#22922

[J.P. Delport]

See osgscreencapture example or search for screencapturehandler.

jp

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[Danny Lesnik]

Hi,

I tried the following code

Code:

osg::ref_ptr<osg::Image> shot = new osg::Image();
shot->allocateImage(640, 480, 24, GL_RGB, GL_UNSIGNED_BYTE);
osg::ref_ptr<osg::Camera> camera = _viewer->getCamera();
_viewer->frame();
camera->attach(osg::Camera::COLOR_BUFFER, shot.get());
osgDB::writeImageFile(*shot, "test.png" );

but still black image. How can I solve the issue.

Thank you!

Cheers,
Danny

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http://forum.openscenegraph.org/viewtopic.php?p=23033#23033

[J.P. Delport]

Hi,

try attach before frame. I'm not sure why you want to call frame
yourself, is this part of a larger app?

jp

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[Trajce Nikolov]

you have to render the scene first then save the image. Have a look at osgprerender examples. Mimic the code and save the image from the Camera DrawCallback

Nick

http://www.linkedin.com/in/tnick

[Danny Lesnik]

Hi,

This is activeX control and inside the contol I have a method which prints screenshot.

This is how I do initiate control AND all OSG instances:

Code:

int ViewerCtrl::OnCreate(LPCREATESTRUCT lpCreateStruct)
{
if (COleControl::OnCreate(lpCreateStruct) == -1)
return -1;

RECT rect;
GetWindowRect(&rect);

WCHAR str[255];
swprintf(str, L"(%d,%d) - (%d,%d)", rect.left,rect.top,rect.right,rect.bottom);

// Set window traits and gc

// Set root node of the scene
_root = new osg::Group;
_viewer->setSceneData( _root.get() );
_viewer->realize();

WS_CHILD|WS_VISIBLE|BS_PUSHBUTTON, CRect(01, 1, 50, 50), this, 1000);

// Create a thread for the simulation loop
_beginthread(&RenderThread, 0, _viewer);
return 0;
}

and this is how do I take screenshot:

Code:

VARIANT_BOOL ViewerCtrl::SaveScreenshot(LPCTSTR name)
{
AFX_MANAGE_STATE(AfxGetStaticModuleState());

CW2A tmpStr(name);

osg::ref_ptr<osg::Image> shot = new osg::Image();
shot->allocateImage(640, 480, 24, GL_RGB, GL_UNSIGNED_BYTE);
osg::ref_ptr<osg::Camera> camera = _viewer->getCamera();
_viewer->frame();
camera->attach(osg::Camera::COLOR_BUFFER, shot.get());
osgDB::writeImageFile(*shot, "test.png" );

//osgViewer::ScreenCaptureHandler* scrn = new osgViewer::ScreenCaptureHandler();
//osgViewer::ScreenCaptureHandler::WriteToFile* captureOper = new osgViewer::ScreenCaptureHandler::WriteToFile(tmpStr.m_szBuffer, "png");
//scrn->setCaptureOperation(capt()ureOper);
//scrn->captureNextFrame(*_viewer);
//_viewer->frame();
return VARIANT_TRUE;
}

so any clue or suggestion is welcomed.
Thank you!

Cheers,
Danny

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[Ralph Kern]

Hi Danny,

you have to attach the image first and then draw the frame:

> osg::ref_ptr<osg::Image> shot = new osg::Image();
> shot->allocateImage(640, 480, 24, GL_RGB, GL_UNSIGNED_BYTE);
> osg::ref_ptr<osg::Camera> camera = _viewer->getCamera();

> camera->attach(osg::Camera::COLOR_BUFFER, shot.get());

> _viewer->frame();
> osgDB::writeImageFile(*shot, "test.png" );
> camera->attach(osg::Camera::COLOR_BUFFER, NULL);

The image is copied from the frame buffer at the end of the frame() call.

regards Ralph

[Danny Lesnik]

Hi,

camera->attach(osg::Camera::COLOR_BUFFER, NULL);

Gives me
Error C2668: 'osg::Camera::attach' : ambiguous call to overloaded function

If I replace it with:

camera->attach(osg::Camera::COLOR_BUFFER, shot.get());

I still get black image.

What might be the problem?

Thank you!

Cheers,
Danny

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