How to grab the Framebuffer in QOpenGLWidget class.

BPrasad

HI,
I am trying to grab the framebuffer in QOpenGLWidget Class. But for some reason I am getting the Empty QImage. Below is my code. I am using FrameBufferObject. Anything wrong? Because I want the pixels to render in my OpenGL context.

saveBackBuffer()
{
_bSavingBackBuffer = true;

 QString fileName("C:\\Users\\ey617e\\Desktop\\yourFile.png");
 QFile file(fileName);
 file.open(QIODevice::WriteOnly);

 glReadBuffer(GL_BACK);
  
  makeCurrent();
  QOpenGLFramebufferObjectFormat format;
  format.setAttachment(QOpenGLFramebufferObject::CombinedDepthStencil);
  QOpenGLFramebufferObject * fbo = new 
  QOpenGLFramebufferObject(_scrWidth, _scrHeight, format);
  fbo->bind();
  paintGL();

 _savedBackBuffer = fbo->toImage();
 _savedBackBuffer.save(file.fileName(), "PNG");
  fbo->release();

}

paintGL()
{
QOpenGLPaintDevice fboPaintDev(_scrWidth, _scrHeight);
QPainter painter(&fboPaintDev);
painter.setRenderHints(QPainter::Antialiasing | QPainter::TextAntialiasing);

painter.beginNativePainting();

drawDisplayLists(_underIllusDisplayLists);
drawDisplayLists(_illusDisplayLists);

painter.endNativePainting();

painter.end();

}

SGaist

Hi,

Taking out your image saving code, are you getting anything rendered on your widget ?

BPrasad

Yes It is getting rendered.

SGaist

@BPrasad said in How to grab the Framebuffer in QOpenGLWidget class.:

QOpenGLFramebufferObject

Are you sure that it is valid ?