OpenGL于MFC使用汇总（三）——离屏渲染

有时直接创建OpenGL形式不适合，或者干脆不同意然后创建一个表单，正如我现在这个项目，创建窗体不显示，它仅限于主框架。而我只是ActiveX里做一些相关工作，那仅仅能用到OpenGL的离屏渲染技术了~即不直接绘制到窗体上，而是绘制到一张位图上。然后再次调用这张位图实现兴许的工作。

以下就总结怎么使用所谓的“离屏渲染”。

    const int WIDTH = 500;const int HEIGHT = 500;// Create a memory DC compatible with the screenHDC hdc = CreateCompatibleDC(0);if (hdc == 0) cout<<"Could not create memory device context";// Create a bitmap compatible with the DC// must use CreateDIBSection(), and this means all pixel ops must be synchronised// using calls to GdiFlush() (see CreateDIBSection() docs)BITMAPINFO bmi = {{ sizeof(BITMAPINFOHEADER), WIDTH, HEIGHT, 1, 32, BI_RGB, 0, 0, 0, 0, 0 },{ 0 }};unsigned char *pbits; // pointer to bitmap bitsHBITMAP hbm = CreateDIBSection(hdc, &bmi, DIB_RGB_COLORS, (void **) &pbits,0, 0);if (hbm == 0) cout<<"Could not create bitmap";//HDC hdcScreen = GetDC(0);//HBITMAP hbm = CreateCompatibleBitmap(hdcScreen,WIDTH,HEIGHT);// Select the bitmap into the DCHGDIOBJ r = SelectObject(hdc, hbm);if (r == 0) cout<<"Could not select bitmap into DC";// Choose the pixel formatPIXELFORMATDESCRIPTOR pfd = {sizeof (PIXELFORMATDESCRIPTOR), // struct size1, // Version numberPFD_DRAW_TO_BITMAP | PFD_SUPPORT_OPENGL, // use OpenGL drawing to BMPFD_TYPE_RGBA, // RGBA pixel values32, // color bits0, 0, 0, // RGB bits shift sizes...0, 0, 0, // Don't care about them0, 0, // No alpha buffer info0, 0, 0, 0, 0, // No accumulation buffer32, // depth buffer bits0, // No stencil buffer0, // No auxiliary buffersPFD_MAIN_PLANE, // Layer type0, // Reserved (must be 0)0, // No layer mask0, // No visible mask0, // No damage mask};int pfid = ChoosePixelFormat(hdc, &pfd);if (pfid == 0) cout<<"Pixel format selection failed";// Set the pixel format// - must be done *after* the bitmap is selected into DCBOOL b = SetPixelFormat(hdc, pfid, &pfd);if (!b) cout<<"Pixel format set failed";// Create the OpenGL resource context (RC) and make it current to the threadHGLRC hglrc = wglCreateContext(hdc);if (hglrc == 0) cout<<"OpenGL resource context creation failed";wglMakeCurrent(hdc, hglrc);// Draw using GL - remember to sync with GdiFlush()GdiFlush();/*详细的绘制函数~~~~~~~~~~~~~~我就不写了*/// Clean upwglDeleteContext(hglrc); // Delete RCSelectObject(hdc, r); // Remove bitmap from DCDeleteObject(hbm); // Delete bitmapDeleteDC(hdc); // Delete DC

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