Save a portion of my program’s own window to a bitmap file using mfc/win32

Within my mfc program, I need to programmatically capture a portion of that program’s own window, then save it out as a file (bmp or jpg etc). How to do this without using 3rd party library开发者_如何学Go?

Here is a comprehensive sample project that provides an example of saving an image of a window to a bitmap: http://www.codeguru.com/cpp/g-m/gdi/capturingimages/article.php/c11231/.