我正在尝试获得一个透明的 SDL_Surface （在其上粘贴半透明矩形），这就是我所做的：
surface := SDL_CreateRGBSurface(SDL_SWSURFACE, XMAX*TILE_SIZE,
YMAX*TILE_SIZE, BPP, 0, 0, 0, SDL_ALPHA_TRANSPARENT);
SDL_FillRect(surface, nil, SDL_MapRGBA(surface^.format, 0, 0, 0, 0));
这仍然不起作用，我得到的表面是黑色而不是透明的。任何想法？
奖励：为了避免多个半透明矩形相互重叠，有什么办法可以删除这些矩形，然后对新的矩形进行 blit（无需再次对背景进行 blitting ...）？
From looking at the docs for SDL_CreateRGBSurface, I think you need to replace SDL_SWSURFACE with SDL_SRCALPHA.
For the bonus part, you might try first to get hardware acceleration working... But if that's not an option and you're willing to spend some memory:
First, before drawing a rectangle, make a copy of the pixels underneath it.
To erase the topmost rectangle you simply re-blit the stored background image.
To erase any other rectangle, you re-blit its background, then redraw the overlapping portions of the rectangles on top of it from back to front.