Simple grayscale mandelbrot set visualization outputted in PGM format.

mandelbrot.c

#include <stdio.h>
#include <stdint.h>
#include <complex.h>

#define MAX_ITERATIONS 80

#define REAL_START -2
#define REAL_END 1
#define IMAG_START -1
#define IMAG_END 1

#define IMAGE_WIDTH 1920
#define IMAGE_HEIGHT 1080

static uint_fast8_t iterations(const double x, const double y) {
    uint_fast8_t n = 0;
    double complex c = (REAL_START + (x / IMAGE_WIDTH) * (REAL_END - REAL_START)) +
                       (IMAG_START + (y / IMAGE_HEIGHT) * (IMAG_END - IMAG_START)) * I;

    for (double complex z = 0; cabs(z) <= 2 && n < MAX_ITERATIONS; z = z * z + c, ++n);

    return n;
}

int main(void) {
    printf("P2\n");
    printf("%d %d\n", IMAGE_WIDTH, IMAGE_HEIGHT);
    printf("255\n");

    for (double y = 0; y < IMAGE_HEIGHT; ++y) {
        for (double x = 0; x < IMAGE_WIDTH; ++x) {
            const uint_fast8_t n = iterations(x, y);
            const uint_fast8_t color = 255 - (n * 255 / MAX_ITERATIONS);

            if (x > 0) printf(" ");
            printf("%d", color);
        }
        printf("\n");
    }

    return 0;
}