bitwise or + circles and squares fractal

// circles and squares fractals + bitwise or, video https://youtu.be/6HzbCWrIqSY
// tgawrite: https://github.com/donbright/piliko/tgawrite
// code by don bright http://github.com/donbright
// Wildberger's Rational Trig ( https://www.youtube.com/watch?v=kRHKbJMm6xE	)
// Santiago Zubieta's art ( https://twitter.com/zubie7a ), http://imgur.com/a/epJxG
#include <SDL.h>
#include <stdio.h>
#include "tgawrite.h"

#define pixelsize 4
Uint32 pixels[256*256*pixelsize];
struct pixl8_t {
	Uint8 blue,green,red,alpha;
};

void quitf() {
	printf("%s\n",SDL_GetError() );
	exit(0);
}


static Uint32 frameno = 0;
void dumptga( Uint32*pixels, Uint16 w, Uint16 h ) {
	char fname[20];
	sprintf(fname,"tmp%06d.tga",frameno++);
	FILE *f = fopen( fname, "wb" );
	tgawrite( pixels, w, h, f );
	fclose(f);
	printf("wrote %s\n",fname);
}

int main( int argc, char* args[] )
{
	if( SDL_Init( SDL_INIT_VIDEO ) < 0 ) quitf();
	if( !SDL_SetHint( SDL_HINT_RENDER_SCALE_QUALITY, "1" ) ) quitf();
	SDL_Window *window = SDL_CreateWindow( "mpixel",
		SDL_WINDOWPOS_UNDEFINED,
		SDL_WINDOWPOS_UNDEFINED,
		256,256,
		SDL_WINDOW_SHOWN );
	if (!window) quitf();
	SDL_Renderer* renderer = SDL_CreateRenderer( window, -1, SDL_RENDERER_ACCELERATED );
	if (!renderer) quitf();
	SDL_SetRenderDrawColor( renderer, 0, 0, 0, 255 );
	SDL_RenderClear( renderer );
	// http://gamedev.stackexchange.com/questions/87727/sdl-updatetexture-is-slow
	SDL_Texture* texture = SDL_CreateTexture(renderer,
                               SDL_PIXELFORMAT_ARGB8888,
                               SDL_TEXTUREACCESS_STREAMING,
                               256, 256);
	if( !texture ) quitf();
	bool quit = false;
	while (!quit)
	{
		SDL_Event event;
		while( SDL_PollEvent( &event ) )
		{
			if( event.type == SDL_QUIT ) quit = true;
			if( event.type == SDL_KEYDOWN ) {
				if ( event.key.keysym.sym == SDLK_ESCAPE ) quit = true;
			}
		}
		Uint8 tmp;
		for (Uint32 i=0;i<256;i++) {
			for (Uint32 j=0;j<256;j++) {
				struct pixl8_t *p;
				p = (struct pixl8_t *)&pixels[j*256+i];
				p->red += (i*i)|(j*j);
				//p->green = 2*i*j;
				p->blue = p->red; //= i*i+j*j;
				p->alpha = 255;
				//printf("%i\n",i);
			}
		}
		dumptga( pixels, 256, 256 );
		SDL_Delay(180);
		SDL_UpdateTexture( texture, NULL, pixels, 256 * pixelsize);
		SDL_RenderCopy( renderer, texture, NULL, NULL );
		SDL_RenderPresent( renderer );
	}
	SDL_DestroyTexture( texture );
	SDL_DestroyRenderer( renderer );
	SDL_DestroyWindow( window );
	SDL_Quit();
	return 0;
}