Re: reading pixels from a TARGET texture

* do you means that the current GL_RenderReadPixels does not work ?

------------------

Yes, If you want to read pixels from SDL_TEXTUREACCESS_TARGET's SDL_texture,
current GL_RenderReadPixels will work  unsuccessfully. Of course,
GL_RenderReadPixels is corresponding to Open GL, for example Microsoft
Windows with SDL_WINDOW_OPENGL. If your app use OpenGL ES2, for example iOS
and Android, you require modify GLES2_RenderReadPixels. Their modification
are the same.

 

* the doc says "WARNING: This is a very slow operation, and should not

  be used frequently." Is this still the case with your version ?

------------------

This still the case with my version, modify don't touch that. You should
absolutely not use SDL_RenderReadPixels(), ever, for anything other than
screenshots and the like.

 

* Ideally I'd rather use an "official" method. Will these changes be

  included in the official SDL2 ?

------------------

I think that next official SDL2 will fix this BUG. Of course, I hope to
patch code to official SDL2, especial BLE.

 

 

If you want read pixels from tex(it's type must be
SDL_TEXTUREACCESS_TARGET), you can write below code.

int RenderReadPixels (SDL_Renderer* renderer, const SDL_Rect* rect,

                          Uint32 format, void* pixels, int pitch,
SDL_Texture* tex)

{

   // assume current target is NULL.

   int result ;

   SDL_Rect dst = {0, 0, rect->w, rect->h} ;

   // Since want to read from tex, should set it to target.

   SDL_SetRenderTarget(renderer, tex) ;

   // pitch = dst.w * byte of one pixel. not tex'width * byte of pixel.

   result = SDL_RenderReadPixels(renderer, &dst, format, pixels, pitch);

 

   // recover target to NULL.

   SDL_SetRenderTarget (renderer, NULL) ;

   return result ;

}

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