code/mandelbrot/mandelbrot.c

#include <stdio.h>
#include "../libpng/img.h"
#include "config.h"




double map(int value, int min, int max, int map_min, int map_max)
{
	double R = (double) (map_max - map_min) / (double) (max - min);
	double y = map_min + (value * R) + R;
	return y;
}

int mandelbrot_pix(double x, double y, int bail_out, int max_iter)
{
	int k;
	double  real, imaginary, x2, y2;
	
	x2 = x;
	y2 = y;

	// iterate a^2 - b^2 + 2ab
	for (k = 0; k < max_iter; k++) {
		// a^2 - b^2
		real = x * x - y * y;
		// 2ab
		imaginary = 2 * x * y;

		// x = real + c
		x = real + x2;
		// y = imaginary + c
		y = imaginary +y2;

		if ((x * x + y * y) >
			bail_out) {
			return k;
		}
	}
	return max_iter;

}

void mandelbrot(double *field, int w, int h, int bail_out, int max_iter)
{
	double xPrime, yPrime;
	int x, y, k;
	for (x = 0; x < w; x++) {
		for (y = 0; y < h; y++) 
		{
			xPrime = map(x, 0, w, -2, 2);
			yPrime = map(y, 0, h, -2, 2);
			mandelbrot_pix(xPrime, yPrime, bail_out, max_iter);
		}
	}
}

int main(int argc, char **argv)
{

	double *pix_field;

	pix_field = malloc(WIDTH * HEIGHT * sizeof(double));

	mandelbrot(pix_field, WIDTH, HEIGHT, BAIL_OUT, MAX_ITER);

	pix_row rows[WIDTH];
	pix p;

	char filename[30];
	image img;
	p.r = 200;
	p.g = 200;
	p.b = 200;

	for (int i = 0; i < WIDTH; i++) {
		rows[i].p = malloc(HEIGHT * sizeof(pix));
		for (int j = 0; j < HEIGHT; j++) {
			p.r =
			    map(pix_field[i * HEIGHT + j], 0, MAX_ITER, 0,
				255);
			p.g =
			    map(pix_field[i * HEIGHT + j], 0, MAX_ITER, 0,
				255);
			p.b =
			    map(pix_field[i * HEIGHT + j], 0, MAX_ITER, 0,
				255);
			rows[i].p[j] = p;
		}
	}
	sprintf(filename, "mandel.png");
	img = initialize_png("mandelbrot", filename, WIDTH, HEIGHT);
	write_image(&img, rows);
	finish_image(&img);
	for (int i = 0; i < WIDTH; i++) {

		free(rows[i].p);
	}

	free(pix_field);

	return (0);
}