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

只使用给定的SDL_Window *和SDL_Renderer *，如何在SDL 2.0中创建和保存屏幕截图？

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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

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If you are using OpenGL with SDL2 you can call glReadPixels directly instead of using the info surface and renderer. Here is an example (without error checking).

void Screenshot(int x, int y, int w, int h, const char * filename)
{
    unsigned char * pixels = new unsigned char[w*h*4]; // 4 bytes for RGBA
    glReadPixels(x,y,w, h, GL_RGBA, GL_UNSIGNED_BYTE, pixels);

    SDL_Surface * surf = SDL_CreateRGBSurfaceFrom(pixels, w, h, 8*4, w*4, 0,0,0,0);
    SDL_SaveBMP(surf, filename);

    SDL_FreeSurface(surf);
    delete [] pixels;
}

Here's the SDL wiki page with an example of setting up the window and an OpenGL context.

链接地址: http://www.djcxy.com/p/67578.html

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