Provided by: libsdl3-doc_3.2.8+ds-1_all 

NAME
SDL_RenderReadPixels - Read pixels from the current rendering target.
HEADER FILE
Defined in SDL3/SDL_render.h
SYNOPSIS
#include "SDL3/SDL.h" SDL_Surface * SDL_RenderReadPixels(SDL_Renderer *renderer, const SDL_Rect *rect);
DESCRIPTION
The returned surface contains pixels inside the desired area clipped to the current viewport, and should be freed with SDL_DestroySurface (). Note that this returns the actual pixels on the screen, so if you are using logical presentation you should use SDL_GetRenderLogicalPresentationRect () to get the area containing your content. WARNING : This is a very slow operation, and should not be used frequently. If you're using this on the main rendering target, it should be called after rendering and before SDL_RenderPresent ().
FUNCTION PARAMETERS
renderer the rendering context. rect an SDL_Rect structure representing the area to read, which will be clipped to the current viewport, or NULL for the entire viewport.
RETURN VALUE
( SDL_Surface *) Returns a new SDL_Surface on success or NULL on failure; call SDL_GetError () for more information.
THREAD SAFETY
This function should only be called on the main thread.
AVAILABILITY
This function is available since SDL 3.2.0. Simple Directmedia Layer SDL 3.2.8 SDL_RenderReadPixels(3)