Generate a wallpaper from random non-intersecting circles

circlewallpapergen.cpp

#include <cmath>
#include <algorithm>
#include <iostream>
#include <tuple>
#include <vector>

using namespace std;

random_device rd;
mt19937_64 gen(rd());
uniform_real_distribution<double> dist(0.0, 1.0);
uniform_int_distribution<int> rgb(0, 255);

vector<tuple<double, double, double>> circles;

tuple<double, double, double> getxyr(double xmax, double ymax, double rmax) {
  double x = dist(gen) * xmax;
  double y = dist(gen) * ymax;

  double r = rmax;
  for (int i = 0; i < circles.size(); ++i) {
    double cdist = hypot(x - get<0>(circles[i]), y - get<1>(circles[i]));
    r = min(r, abs(cdist - get<2>(circles[i])));
  }
  r *= (dist(gen) + 1) / 2.5;

  circles.push_back(make_tuple(x, y, r));
  return make_tuple(x, y, r);
}

string rgbtostring(int r, int g, int b) {
  string ret = "";
  int clr = r * 65536 + g * 256 + b;
  for (int i = 0; i < 6; ++i, clr >>= 4) {
    int cur = clr & 15;
    if (cur < 10) {
      ret = (char)(cur + '0') + ret;
    } else {
      ret = (char)(cur - 10 + 'A') + ret;
    }
  }
  return ret;
}

int main() {
  cout << "set size ratio -1\n";
  cout << "set xrange[0:16]\n";
  cout << "set yrange[0:9]\n";
  cout << "set lmargin 0\n";
  cout << "set rmargin 0\n";
  cout << "set bmargin 0\n";
  cout << "set tmargin 0\n";
  cout << "unset border\n";
  cout << "unset tics\n";
  cout << "set style fill transparent solid 0.8 noborder\n";
  cout << "set term pngcairo enhanced size 1920,1080\n";
  cout << "set output 'circlewallpaper.png'\n";
  for (int i = 0; i < 5000; ++i) {
    double x, y, r;
    tie(x, y, r) = getxyr(16, 9, 5);
    string col = rgbtostring(rgb(gen), rgb(gen), rgb(gen));
    cout << "set object circle at " << x << "," << y << " size " << r
         << " fc rgb '#" << col << "'\n";
  }
  cout << "plot 1/0 notitle\n";
  cout << "set output\n";
  return 0;
}