Win32 C++ or MFC Sprite Animation

If you need masking then you always have to redraw the background as well before blitting your masked image so you will have to use double buffering to avoid flickering (you always draw to a bitmap instead of the window and then blit the bitmap to the window when all the drawing is ready).
So, you create your bitmap (the backsurface) to draw on and then when you get a WM_PAINT message in your window you start drawing on this bitmap: first you draw the background with a bitblt/SRCCOPY, then you draw the appropriate sprite animation frame like this: http://www.winprog.org/tutorial/transparency.html and then you draw the whole bitmap to your window with bitblt/SRCCOPY. If you need frequent updates then setup a WM_TIMER message for your window with the SetTimer() call and then from your periodically called WM_TIMER event handler you can force a WM_PAINT message by calling InvalidateRect(). I wouldn't use WM_TIMER is the accuracy I needed was beyond 50-100 frame/sec but I think that must be enough for your animation.