Re: reading pixels from a TARGET texture

Sanette wrote:
> What is the best way to obtain this pixel array ?

You can use SDL_RenderReadPixels but there are a couple of problems with that approach:
	The API is buggy.  For example with some renderers it will return the image upside-down (https://bugzilla.libsdl.org/show_bug.cgi?id=2740)!

	The API can be very slow, especially if the target texture is significantly larger than the window.

To work around the first issue, and to ameliorate the second, I use this slightly more complex method (when the rectangle you want to read is no larger than the window):


Code:
int RenderReadPixels (SDL_Renderer* renderer, const SDL_Rect* rect,
                          Uint32 format, void* pixels, int pitch)
{
	int result ;
	SDL_Rect dst = {0, 0, rect->w, rect->h} ;
	SDL_Texture *tex = SDL_GetRenderTarget (renderer) ;
	SDL_SetRenderTarget (renderer, NULL) ;
	SDL_RenderCopy (renderer, tex, rect, &dst) ;
	result = SDL_RenderReadPixels (renderer, &dst, format, pixels, pitch) ;
	SDL_SetRenderTarget (renderer, tex) ;
	return result ;
}


Richard.

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