Pixel copy Opengl DIB

void CopyPBufferToImage(int width, int height)
{
    // Copy the contents of the framebuffer - which in our case is our pixel buffer -
    // to our bitmap image (dummy target) in local system memory. Notice that we also need
    // to invert the pbuffer's pixel data since OpenGL by default orients the
    // bitmap image bottom up. Our Windows DIB wrapper expects images to be
    // top down in orientation.

    static BYTE *pixels = new BYTE[width * height * 4];
    memset(pixels, 0, width * height * 4);

    glPixelStorei(GL_PACK_ALIGNMENT, 1);
    glReadPixels(0, 0, width, height, GL_BGRA_EXT, GL_UNSIGNED_BYTE, pixels);

    for (int i = 0; i < height; ++i)
    {
        memcpy(&m_img.pPixels[m_img.pitch * i],
            &pixels[((height - 1) - i) * (width * 4)],
            width * 4);
    }
}