Task: Voronoi diagram

C: #include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define N_SITES 150
double site[N_SITES][2];
unsigned char rgb[N_SITES][3];

int size_x = 640, size_y = 480;

inline double sq2(double x, double y)
{
	return x * x + y * y;
}

#define for_k for (k = 0; k < N_SITES; k++)
int nearest_site(double x, double y)
{
	int k, ret = 0;
	double d, dist = 0;
	for_k {
		d = sq2(x - site[k][0], y - site[k][1]);
		if (!k || d < dist) {
			dist = d, ret = k;
		}
	}
	return ret;
}


int at_edge(int *color, int y, int x)
{
	int i, j, c = color[y * size_x + x];
	for (i = y - 1; i <= y + 1; i++) {
		if (i < 0 || i >= size_y) continue;

		for (j = x - 1; j <= x + 1; j++) {
			if (j < 0 || j >= size_x) continue;
			if (color[i * size_x + j] != c) return 1;
		}
	}
	return 0;
}

#define AA_RES 4 
void aa_color(unsigned char *pix, int y, int x)
{
	int i, j, n;
	double r = 0, g = 0, b = 0, xx, yy;
	for (i = 0; i < AA_RES; i++) {
		yy = y + 1. / AA_RES * i + .5;
		for (j = 0; j < AA_RES; j++) {
			xx = x + 1. / AA_RES * j + .5;
			n = nearest_site(xx, yy);
			r += rgb[n][0];
			g += rgb[n][1];
			b += rgb[n][2];
		}
	}
	pix[0] = r / (AA_RES * AA_RES);
	pix[1] = g / (AA_RES * AA_RES);
	pix[2] = b / (AA_RES * AA_RES);
}

#define for_i for (i = 0; i < size_y; i++)
#define for_j for (j = 0; j < size_x; j++)
void gen_map()
{
	int i, j, k;
	int *nearest = malloc(sizeof(int) * size_y * size_x);
	unsigned char *ptr, *buf, color;

	ptr = buf = malloc(3 * size_x * size_y);
	for_i for_j nearest[i * size_x + j] = nearest_site(j, i);

	for_i for_j {
		if (!at_edge(nearest, i, j))
			memcpy(ptr, rgb[nearest[i * size_x + j]], 3);
		else	
			aa_color(ptr, i, j);
		ptr += 3;
	}

	
	for (k = 0; k < N_SITES; k++) {
		color = (rgb[k][0]*.25 + rgb[k][1]*.6 + rgb[k][2]*.15 > 80) ? 0 : 255;

		for (i = site[k][1] - 1; i <= site[k][1] + 1; i++) {
			if (i < 0 || i >= size_y) continue;

			for (j = site[k][0] - 1; j <= site[k][0] + 1; j++) {
				if (j < 0 || j >= size_x) continue;

				ptr = buf + 3 * (i * size_x + j);
				ptr[0] = ptr[1] = ptr[2] = color;
			}
		}
	}

	printf("P6\n%d %d\n255\n", size_x, size_y);
	fflush(stdout);
	fwrite(buf, size_y * size_x * 3, 1, stdout);
}

#define frand(x) (rand() / (1. + RAND_MAX) * x)
int main()
{
	int k;
	for_k {
		site[k][0] = frand(size_x);
		site[k][1] = frand(size_y);
		rgb [k][0] = frand(256);
		rgb [k][1] = frand(256);
		rgb [k][2] = frand(256);
	}

	gen_map();
	return 0;
}




Go: package main

import (
    "fmt"
    "image"
    "image/color"
    "image/draw"
    "image/png"
    "math/rand"
    "os"
    "time"
)

const (
    imageWidth  = 300
    imageHeight = 200
    nSites      = 10
)

func main() {
    writePngFile(generateVoronoi(randomSites()))
}

func generateVoronoi(sx, sy []int) image.Image {
    
    sc := make([]color.NRGBA, nSites)
    for i := range sx {
        sc[i] = color.NRGBA{uint8(rand.Intn(256)), uint8(rand.Intn(256)),
            uint8(rand.Intn(256)), 255}
    }

    
    img := image.NewNRGBA(image.Rect(0, 0, imageWidth, imageHeight))
    for x := 0; x < imageWidth; x++ {
        for y := 0; y < imageHeight; y++ {
            dMin := dot(imageWidth, imageHeight)
            var sMin int
            for s := 0; s < nSites; s++ {
                if d := dot(sx[s]-x, sy[s]-y); d < dMin {
                    sMin = s
                    dMin = d
                }
            }
            img.SetNRGBA(x, y, sc[sMin])
        }
    }
    
    black := image.NewUniform(color.Black)
    for s := 0; s < nSites; s++ {
        draw.Draw(img, image.Rect(sx[s]-2, sy[s]-2, sx[s]+2, sy[s]+2),
            black, image.ZP, draw.Src)
    }
    return img
}

func dot(x, y int) int {
    return x*x + y*y
}

func randomSites() (sx, sy []int) {
    rand.Seed(time.Now().Unix())
    sx = make([]int, nSites)
    sy = make([]int, nSites)
    for i := range sx {
        sx[i] = rand.Intn(imageWidth)
        sy[i] = rand.Intn(imageHeight)
    }
    return
}

func writePngFile(img image.Image) {
    f, err := os.Create("voronoi.png")
    if err != nil {
        fmt.Println(err)
        return
    }
    if err = png.Encode(f, img); err != nil {
        fmt.Println(err)
    }
    if err = f.Close(); err != nil {
        fmt.Println(err)
    }
}