与sdl2的透明度

Question

我实际上试图在一个完全透明的窗口上显示一个.png图像（带有透明背景）但是当我执行我的程序时，我的图像是黑色背景。

不知道如何移除这个黑色层。

提前致谢

int main(void)
{
    bool            quit = false;
    SDL_Event       event;

    SDL_Window      *window;
    SDL_Renderer    *renderer;
    SDL_Surface     *image;
    SDL_Texture     *texture;

    struct dirent   **fileslist;
    char            **state;
    char            locationimg[15];

    checkfiles();
    scandir("img/", &fileslist, 0, alphasort);
    states(&state);

    if (SDL_Init(SDL_INIT_VIDEO) != 0)
    {
        fprintf(stdout, "Initialisation of SDL failed (%s)\n", SDL_GetError());
        return (-1);
    }

    window = SDL_CreateWindow("test", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, 128, 128, SDL_WINDOW_BORDERLESS);
    if (!window)
        fprintf(stderr, "Error in creation of window: %s\n", SDL_GetError());

    renderer = SDL_CreateRenderer(window, -1, 0);
    strcpy(locationimg, "img/");
    image = IMG_Load(strcat(locationimg, fileslist[state[0][0]]->d_name));
    texture = SDL_CreateTextureFromSurface(renderer, image);
    if (!image)
    {
        fprintf(stderr, "IMG_Load: %s\n", IMG_GetError());
        return (-1);
    }

    while (!quit)
    {
        SDL_WaitEvent(&event);

        switch (event.type)
        {
            case SDL_MOUSEBUTTONDOWN:
                quit = true;
                break;
        }

        SDL_RenderCopy(renderer, texture, NULL, NULL);
        SDL_RenderPresent(renderer);
    }

    SDL_DestroyTexture(texture);
    SDL_FreeSurface(image);
    SDL_DestroyRenderer(renderer);
    SDL_DestroyWindow(window);
    SDL_Quit();

    return (0);
}