如何清除SDL_Surface以替换另一个？

#include <SDL.h>
#include <SDL_image.h>

int main(int argc, char* argv[]) {
    SDL_Init(SDL_INIT_VIDEO);
    SDL_Surface* screen = SDL_SetVideoMode(640, 480, 32, SDL_HWSURFACE | SDL_DOUBLEBUF);

    SDL_Surface* surface = SDL_CreateRGBSurface(SDL_HWSURFACE, 640, 480, 32, 0, 0, 0, 0);
    SDL_FillRect(surface, NULL, SDL_MapRGB(screen->format, 255, 255, 255));

    SDL_BlitSurface(surface, NULL, screen, NULL);
    SDL_Flip(screen);

    SDL_FreeSurface(surface);
    SDL_Quit();
    return 0;
}

SDL_Surface* image = SDL_LoadBMP("image.bmp");
SDL_BlitSurface(image, NULL, screen, NULL);
SDL_Flip(screen);
SDL_FreeSurface(image);