How do I take and save a BMP screenshot in SDL 2?

Question

Using just a given SDL_Window* and SDL_Renderer*, how can I create and save a screenshot in SDL 2.0?

Answer 1

Below is a function for saving a screenshot in SDL 2 taken from a library I'm currently writing.

bool saveScreenshotBMP(std::string filepath, SDL_Window* SDLWindow, SDL_Renderer* SDLRenderer) {
    SDL_Surface* saveSurface = NULL;
    SDL_Surface* infoSurface = NULL;
    infoSurface = SDL_GetWindowSurface(SDLWindow);
    if (infoSurface == NULL) {
        std::cerr << "Failed to create info surface from window in saveScreenshotBMP(string), SDL_GetError() - " << SDL_GetError() << "\n";
    } else {
        unsigned char * pixels = new (std::nothrow) unsigned char[infoSurface->w * infoSurface->h * infoSurface->format->BytesPerPixel];
        if (pixels == 0) {
            std::cerr << "Unable to allocate memory for screenshot pixel data buffer!\n";
            return false;
        } else {
            if (SDL_RenderReadPixels(SDLRenderer, &infoSurface->clip_rect, infoSurface->format->format, pixels, infoSurface->w * infoSurface->format->BytesPerPixel) != 0) {
                std::cerr << "Failed to read pixel data from SDL_Renderer object. SDL_GetError() - " << SDL_GetError() << "\n";
                delete[] pixels;
                return false;
            } else {
                saveSurface = SDL_CreateRGBSurfaceFrom(pixels, infoSurface->w, infoSurface->h, infoSurface->format->BitsPerPixel, infoSurface->w * infoSurface->format->BytesPerPixel, infoSurface->format->Rmask, infoSurface->format->Gmask, infoSurface->format->Bmask, infoSurface->format->Amask);
                if (saveSurface == NULL) {
                    std::cerr << "Couldn't create SDL_Surface from renderer pixel data. SDL_GetError() - " << SDL_GetError() << "\n";
                    delete[] pixels;
                    return false;
                }
                SDL_SaveBMP(saveSurface, filepath.c_str());
                SDL_FreeSurface(saveSurface);
                saveSurface = NULL;
            }
            delete[] pixels;
        }
        SDL_FreeSurface(infoSurface);
        infoSurface = NULL;
    }
    return true;
}

Cheers! -Neil