OGRE save render window to image file

Ogre_save_render_window_to_image_file.cpp

// from https://forums.ogre3d.org/viewtopic.php?t=67447

void HDRCtrl::OnBnClickedSaverender()
{
	Ogre::TexturePtr tex = Ogre::TextureManager::getSingleton().createManual(
			"MainRenderTarget", 
			Ogre::ResourceGroupManager::DEFAULT_RESOURCE_GROUP_NAME, 
			Ogre::TextureType::TEX_TYPE_2D, 
			m_w,
			m_h,
			m_d,
			0,
			Ogre::PixelFormat::PF_R8G8B8,
			Ogre::TextureUsage::TU_RENDERTARGET);

	Ogre::RenderTexture *renderTexture = tex->getBuffer()->getRenderTarget();

	renderTexture->addViewport(m_camera);
	int count = renderTexture->getNumViewports();
	
	renderTexture->getViewport(0)->setClearEveryFrame(true);
	renderTexture->getViewport(0)->setBackgroundColour(Ogre::ColourValue::Black);
	renderTexture->getViewport(0)->setOverlaysEnabled(false);

	renderTexture->update();

	// Now save the contents
	renderTexture->writeContentsToFile("./RoomRender.png");
}