使用SDL2显示灰阶格式图片的示例代码

以下是一个使用SDL2显示灰阶格式图片的示例代码，其中假设灰阶图片的宽度为width，高度为height，像素值存储在名为pixels的unsigned char类型数组中：

#include <SDL2/SDL.h>

int main(int argc, char* argv[]) {
    SDL_Window* window = NULL;
    SDL_Surface* surface = NULL;
    SDL_Event event;
    unsigned char* pixels = NULL;
    int width = 640;
    int height = 480;

    if (SDL_Init(SDL_INIT_VIDEO) < 0) {
        printf("SDL could not initialize! SDL_Error: %s\n", SDL_GetError());
        return 1;
    }

    window = SDL_CreateWindow("Gray Image", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, width, height, SDL_WINDOW_SHOWN);
    if (window == NULL) {
        printf("Window could not be created! SDL_Error: %s\n", SDL_GetError());
        return 1;
    }

    surface = SDL_GetWindowSurface(window);
    if (surface == NULL) {
        printf("Surface could not be created! SDL_Error: %s\n", SDL_GetError());
        return 1;
    }

    pixels = (unsigned char*)surface->pixels;

    // 将像素值拷贝到surface中
    for (int i = 0; i < height; i++) {
        for (int j = 0; j < width; j++) {
            int index = i * width + j;
            pixels[index] = pixels[index + 1] = pixels[index + 2] = pixels[index + 3] = pixels[index];
        }
    }

    // 更新surface
    SDL_UpdateWindowSurface(window);

    while (1) {
        if (SDL_PollEvent(&event)) {
            if (event.type == SDL_QUIT) {
                break;
            }
        }
    }

    SDL_DestroyWindow(window);
    SDL_Quit();

    return 0;
}

代码中，先创建一个窗口，然后获取该窗口的表面(surface)并将其存储在指针surface中。接下来，将unsigned char类型数组中的像素值拷贝到surface->pixels中，并将其显示在窗口上。最后，使用SDL_PollEvent函数来处理退出事件，等待用户关闭窗口。