gistfile1.cpp

extern SDL_Renderer * _renderer;

static SDL_bool UI_SaveScreenshotBMP(const char * fileName)
{
    int w = 0;
    int h = 0;
    SDL_GetWindowSize(_window, &w, &h);

    const int bytesPerPixel = 4;
    const int pitch = w * bytesPerPixel;

    std::vector<Uint8> pixels(w * h * bytesPerPixel);
    if (SDL_RenderReadPixels(_renderer, NULL, SDL_PIXELFORMAT_RGB888, &pixels[0], pitch) != 0) {
        string errorMessage = string("Unable to read pixels, reason: ") + SDL_GetError();
        SDL_SetError(errorMessage.c_str());
        return SDL_FALSE;
    }

    SDL_Surface * screen = SDL_CreateRGBSurfaceFrom(
        &pixels[0],
        w, h,
        bytesPerPixel * 8,
        pitch,
        0x00FF0000,
        0x0000FF00,
        0x000000FF,
        0xFF000000);
    if (!screen) {
        string sdlError = SDL_GetError();
        SDL_SetError("Unable to create SDL_Surface for output, reason: %s",
            sdlError.c_str());
        return SDL_FALSE;
    }

    if (SDL_SaveBMP(screen, fileName) != 0) {
        string sdlError = SDL_GetError();
        SDL_SetError("Unable to save BMP to file, \"%s\", reason: %s",
            fileName, sdlError.c_str());
        return SDL_FALSE;
    }

    SDL_Log("Saved screenshot to \"%s\".\n", fileName);
    return SDL_TRUE;
}