Gldrawpixels To Stencil Buffer

Gldrawpixels To Stencil Buffer

I'm creating a image using OpenCV which I would like to use as a stencil.  However, when I upload the image using glDrawPixels and then read it back using glReadPixels,  I only get a fraction of the image.   It is not obvious to me what is the problem since the alignment appears correct.  Help would be appreciated.  The code and images are below.

 

  

 

//---------------------------------------------------------------------

// createStencilBuffer

//---------------------------------------------------------------------

void RenderRadiance::createStencilBuffer(void)

{

cv::Mat stencilImg(_radDim.y,_radDim.x,CV_8UC1);

 

  stencilImg.setTo(0); 

 

  for (size_t i = 0;i < _hPntLst.size();i++)

  {

  HPnt  hPnt = _hPntLst[i];

 

    cv::circle(stencilImg,cv::Point(hPnt._hCen.x,hPnt._hCen.y),(int)_hogelDiameter/2,cv::Scalar(255),-1);

  }

  

  glPixelStorei(GL_UNPACK_ALIGNMENT,1);

  glPixelStorei(GL_UNPACK_ROW_LENGTH,_radDim.x);

  glPixelStorei(GL_UNPACK_SKIP_ROWS,0);

  glPixelStorei(GL_UNPACK_SKIP_PIXELS,0);

 

  glPixelStorei(GL_PACK_ALIGNMENT,1);

  glPixelStorei(GL_PACK_ROW_LENGTH,_radDim.x);

  glPixelStorei(GL_PACK_SKIP_ROWS,0);

  glPixelStorei(GL_PACK_SKIP_PIXELS,0);

 

  glGenRenderbuffers(1,&_renderStencilBuffer);

  glBindRenderbuffer(GL_RENDERBUFFER,_renderStencilBuffer);

  glRenderbufferStorage(GL_RENDERBUFFER,GL_STENCIL_INDEX,_radDim.x,_radDim.y);

 

  glDrawPixels(_radDim.x,_radDim.y,GL_STENCIL_INDEX,GL_UNSIGNED_BYTE,stencilImg.data);

 

  if (1)

  {

  cv::Mat stencilImgRead(_radDim.y,_radDim.x,CV_8UC1);

 

    glReadPixels(0,0,_radDim.x,_radDim.y,GL_STENCIL_INDEX,GL_UNSIGNED_BYTE,stencilImgRead.data);

 

    cv::imwrite("Stencil.png",stencilImg);

    cv::imwrite("StencilGPU.png",stencilImgRead);

  }

}

 

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