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main.cpp

#define STB_IMAGE_WRITE_IMPLEMENTATION

#include <cstdio>
#include <iostream>
#include <vector>
#include <complex>

#include "stb_image.h"
#include "stb_image_write.h"

int main () {

	const int image_width = 256;
	const int image_height = 256;

	std::vector<unsigned char> pixels(image_width * image_height * 4);

	const double center_x = 0.3602404434376143632;
	const double center_y = 0.6413130610648031748;

	double view_width = 5.0;

	for (int n = 0; n < 30; n++) {

		view_width *= 0.5;

		double view_height = view_width * (image_height / image_width);

		for (int y = 0; y < image_height; y++) {

			int x;
			const double ry = double(y) * (view_height / image_height) + center_y - view_height / 2.0;

			#pragma omp parallel for

			for (x = 0; x < image_width; x++) {

				const size_t index = (y * image_width + x) * 4;

				pixels[index + 0] = 0x00;
				pixels[index + 1] = 0x00;
				pixels[index + 2] = 0x00;
				pixels[index + 3] = 0xFF;

				const std::complex<double> c(
					double(x) * (view_width / image_width) + center_x - view_width / 2.0,
					ry
				);

				std::complex<double> z(0.0, 0.0);

				for (int n = 0; n < 1024; n++) {
					z = z * z + c;
					if (std::abs(z) >= 2.0) {
						int b = int(255.0 * double(n) / 1024);
						pixels[index + 0] = b;
						pixels[index + 1] = b;
						pixels[index + 2] = b;
						break;
					}
				}

			}
		}

		char filename[64];
		std::sprintf(filename, "out/%04d.png", n);
		std::cout << "writing " << filename << " ... ";
		stbi_write_png(filename, image_width, image_height, STBI_rgb_alpha, &(*pixels.begin()), 0);
		std::cout << "done.\n";

	}

}