SDL2 像素操作

Question

我需要创建一个窗口，并用颜色填充它的所有像素。这不应该太难，但一个小时左右后我仍然无法让它工作。这是我现在的代码：

#include <SDL2/SDL.h>

int main(int argc, char** argv)
{
    enum {
        WIDTH = 640,
        HEIGHT = 480
    };
    SDL_Window* window = SDL_CreateWindow(
        "SDL test",
        SDL_WINDOWPOS_CENTERED,
        SDL_WINDOWPOS_CENTERED,
        WIDTH,
        HEIGHT,
        SDL_WINDOW_SHOWN
    );
    SDL_Renderer* renderer = SDL_CreateRenderer(window, -1, SDL_RENDERER_ACCELERATED);

    SDL_Texture* texture = SDL_CreateTexture(renderer,
        SDL_PIXELFORMAT_RGBA8888,
        SDL_TEXTUREACCESS_STREAMING,
        WIDTH,
        HEIGHT
    );
    SDL_Surface* surface = SDL_CreateRGBSurface(
        0,
        WIDTH,
        HEIGHT,
        32,
        0x00000000,
        0x00000000,
        0x00000000,
        0xff000000
    );
    Uint32 gray = SDL_MapRGBA(surface->format, 0x1E, 0x1E, 0x1E, 0xFF);
    Uint32 red = SDL_MapRGBA(surface->format, 0xFA, 0x32, 0x32, 0xFF);

    int i, j;
    Uint32* pixels32 = (Uint32*) surface->pixels;
    for (i = 0; i < HEIGHT; ++i)
    {
        for (j = 0; j < WIDTH; ++j)
        {
            pixels32[i * WIDTH + j] = j%10 ? gray : red;
        }
    }
    SDL_UpdateTexture(texture, NULL, surface->pixels, surface->pitch);

    SDL_RenderPresent(renderer);

    int quit = 0;
    SDL_Event event;
    while (!quit)
    {
        while (SDL_PollEvent(&event) != 0)
        {
            if (event.type == SDL_QUIT)
                quit = 1;
        }
    }
    SDL_FreeSurface(surface);
    SDL_DestroyRenderer(renderer);
    SDL_DestroyWindow(window);
    SDL_Quit();

    return 0;
}

但它显示一个白色窗口。我做错了什么？

Answer 1

您创建了一个纹理，但尚未绘制它。为了在表面上绘制它，您仍然需要调用SDL_RenderCopy。