sierpinski.cpp

#include <cmath>
#include <cstdio>
#include <iostream>
#include <string>

#include "include/SDL.h"

enum
{
    /**
    * \brief Window Width
    */
    width = 1366,

    /**
     * \brief Window Height
     */
     height = 768
};

void draw_triangle(SDL_Renderer* renderer, const float x, const float y, const float size) {
	const float half_size = size / 2.0f;
	const float height = half_size * (std::sqrt(3.0f) / 2.0f);

	const int start_x = static_cast<int>(roundf(x));
	const int start_y = static_cast<int>(roundf(y + half_size + 4));

	const int left_x = static_cast<int>(roundf(x - half_size));
	const int left_y = static_cast<int>(roundf(y - height));

	const int right_x = static_cast<int>(roundf(x + half_size));
	const int right_y = static_cast<int>(roundf(y - height));

    SDL_RenderDrawLine(renderer, left_x, left_y, right_x, right_y);
    SDL_RenderDrawLine(renderer, right_x, right_y, start_x, start_y);
    SDL_RenderDrawLine(renderer, start_x, start_y, left_x, left_y);
}

void sierpinski_sieve(SDL_Renderer* renderer, const int n, const float x, const float y, const float size) {
    if (n == 0) {
        draw_triangle(renderer, x, y, size);
    }
    else {
	    const float new_size = size / 2;
        sierpinski_sieve(renderer, n - 1, x, y, new_size);
        sierpinski_sieve(renderer, n - 1, x + new_size, y, new_size);
        sierpinski_sieve(renderer, n - 1, x + new_size / 2, y + new_size, new_size);
    }
}

void clear_screen(SDL_Renderer* renderer) {
    SDL_SetRenderDrawColor(renderer, 23, 23, 23, 255);
    SDL_RenderClear(renderer);
	SDL_RenderPresent(renderer);
}

int main(int argc, char* argv[]) {
    SDL_Init(SDL_INIT_VIDEO);

    SDL_Window* window = SDL_CreateWindow("Sierpinski Triangle", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, width, height, SDL_WINDOW_SHOWN);
    SDL_Renderer* renderer = SDL_CreateRenderer(window, -1, SDL_RENDERER_ACCELERATED);
	clear_screen(renderer);
    int n = 3;
    int ret = 0;
    constexpr SDL_RendererFlip flip = SDL_FLIP_VERTICAL;
    SDL_Texture* texture = SDL_CreateTexture(renderer, SDL_PIXELFORMAT_RGBA8888, SDL_TEXTUREACCESS_TARGET, width, height);
    

    printf("Enter the number of iterations for the Sierpinski Triangle: ");
    std::cin >> n;

    SDL_Event ev;

    while(SDL_WaitEvent(&ev)) {
        if (ev.type == SDL_QUIT) break;

        SDL_SetRenderTarget(renderer, texture);

        // Continue to draw
    	clear_screen(renderer);
        SDL_SetRenderDrawColor(renderer, 190, 190, 190, 255);

        sierpinski_sieve(renderer, n, static_cast<float>(width) / 2 - static_cast<float>(width) / 4, 64, static_cast<float>(width) / 2);

        SDL_SetRenderTarget(renderer, nullptr);
        SDL_RenderCopyEx(renderer, texture, nullptr, nullptr, 0, nullptr, flip);

        SDL_RenderPresent(renderer);
		SDL_Delay(500);

    }
    SDL_Surface* surface = SDL_GetWindowSurface(window);
    SDL_RenderReadPixels(renderer, nullptr, surface->format->format, surface->pixels, surface->pitch);

    const std::string filename = "sierpinski-"+ std::to_string(n) + " levels.png";

	SDL_SaveBMP(surface, filename.c_str());

    SDL_DestroyTexture(texture);
    SDL_FreeSurface(surface);
    SDL_DestroyRenderer(renderer);
    SDL_DestroyWindow(window);
    SDL_Quit();

    std::cout << "Sierpinski Triangle saved as " << filename << std::endl;

    return 0;
}