Introduction to Voronoi diagram and implementation of C language

Voronoi diagrams are widely used in geometry, geography, crystallography, information systems and other disciplines. A Voronoi diagram is a continuous polygon composed of perpendicular bisector that are connected by each adjacent point in the diagram. The points in the diagram belong to the nearest polygon of the point, as shown in:

The corresponding C language implementation code for the Voronoi diagram is as follows:

#include <stdio.h> #include <stdlib.h> #include <string.h> #define N_sites 150double site[n_sites][2] ; unsigned char rgb[n_sites][3]; int size_x = 640, size_y = 480; Inline double sq2 (double x, double y)//square function{return x * x + y * y;} #define For_k for (k = 0; k < n_sites; +)//define for_kint nearest_site (double x, double y)//get the nearest site Id{int k, ret = 0;double D, dist = 0;for_k {D = SQ2 (X-site[k][0], y-site[k][1]), if (!k | | D < dist) {//get the nearest distancedist = d, ret = k;}} return ret;} /* See if a pixel are different from any neighboring ones */int At_edge (int *color, int y, int x) {int I, j, C = color[y * s Ize_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/* Average over 4x4 supersampling grid */void aa_color (unsigned char *pix, int y, int x)//gET color for pix (x, y) {int i, j, n;double r = 0, g = 0, b = 0, XX, yy;for (i = 0; i < aa_res; i++) {yy = y + 1./aa_re S * 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);p ix[1] = g/(Aa_res * aa_res);p ix[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/* at Edge, do anti-alias raster ing */aa_color (PTR, I, j);p tr + = 3;} /* Draw Sites */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);p tr[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 (n), RGB [k][1] = Frand (n), RGB [k][2] = Frand (256);} Gen_map (); return 0;}

Introduction to Voronoi diagram and implementation of C language