从源SDL_Texture中提取SDL_Texture

Question

我有以下功能，从更大的纹理贴图中提取64x64像素的纹理：

SDL_Texture* cropTexture (SDL_Texture* src, int x, int y)
{
    SDL_Texture* dst = SDL_CreateTexture(gRenderer, gSurface->format->format, SDL_TEXTUREACCESS_TARGET, 64, 64);
    SDL_Rect rect = {64 * x, 64 * y, 64, 64};
    SDL_SetRenderTarget(gRenderer, dst);
    SDL_RenderCopy(gRenderer, src, &rect, NULL);

    return dst;
}

现在，当我像这样调用这个函数时：

SDL_Texture* txt_walls [3];
txt_walls[0] = cropTexture (allWalls, 0, 0);
txt_walls[1] = cropTexture (allWalls, 0, 1);
txt_walls[2] = cropTexture (allWalls, 4, 3);

然后txt_walls[2]会产生黑色纹理(或至少未初始化)。

当我添加一行毫无意义的代码时：

SDL_Texture* txt_walls [3];
txt_walls[0] = cropTexture (allWalls, 0, 0);
txt_walls[1] = cropTexture (allWalls, 0, 1);
txt_walls[2] = cropTexture (allWalls, 4, 3);
cropTexture (allWalls, 1, 1); // whatever, ignore the returned object

那么txt_walls2是正确的:这个数组位置的纹理在我的程序中呈现得很好。

cropTexture有什么问题？我在C++和SDL2都是新手。

Answer 1

您需要在裁剪文本之后将呈现目标设置为默认，否则它将继续绘制纹理。在return in cropTexture之前添加以下内容

SDL_SetRenderTarget(gRenderer, NULL);