dump_texture_to_file.c

void dump_texture_to_file(SDL_Renderer *renderer, SDL_Texture *texture, const char *filename)
{
    SDL_Log("%s: ENTERING\n", __func__);

    Uint32 format;
    int access;
    int width;
    int height;

    SDL_QueryTexture(texture, &format, &access, &width, &height);
    SDL_Log("%s: Texture info: Format: %s - Access: %d - Width: %d - Height: %d\n",
            __func__, SDL_GetPixelFormatName(format), access, width, height);

    Uint32 *pixels = malloc(width * height * sizeof(*pixels));
    SDL_RenderReadPixels(renderer, NULL, format, pixels, width);
    SDL_Surface *surface = SDL_CreateRGBSurfaceWithFormatFrom(pixels, width, height, 32, width, format);
    if(!surface)
        SDL_Log("%s: Could not create surface %s\n", __func__, SDL_GetError());

    SDL_Log("%s: Saving texture to file %s\n", __func__, filename);
    SDL_SaveBMP(surface, filename);

    free(pixels);
    SDL_FreeSurface(surface);
    SDL_Log("%s: LEAVING\n", __func__);
}