# include <cstdlib>
# include <iostream>
# include <cmath>

using namespace std;

int main ( );
void color ( int red, int green, int blue );

//****************************************************************************80

int main ( )

//****************************************************************************80
//
//  Purpose:
//
//    MANDELBROT_PPM creates an ASCII PPM image of the Mandelbrot set.
//
//  Notice:
//
//    mandelbrot_ppm.C   by Eric R. Weeks   written 9-28-96
//    weeks@physics.emory.edu
//    http://www.physics.emory.edu/~weeks/
//
//    This program is public domain, but this header must be left intact
//    and unchanged.
//
//  Author:
//
//    Eric Weeks
//
//  Local Parameters:
//
//    Local, int HXRES, the horizontal resolution (number of pixels);
//
//    Local, int HYRES, the vertical resolution (number of pixels);
//
//    Local, int ITERMAX, the number of iterations to carry out.
//
//    Local, double MAGNIFY, the magnification factor.
//
{
  double cx;
  double cy;
  int hx;
  int hxres = 500;
  int hy;
  int hyres = 500;
  int it2;
  int iteration;
  int itermax = 100;
  double magnify = 1.0;
  double x;
  double x_new;
  double y;
  double y_new;
//
//  Write the PPM header.
//
  cout << "P6\n";
  cout << "# CREATOR: Eric R Weeks / mandel program\n";
  cout << hxres << "  " << hyres << " " << 255 << "\n";

  for ( hy = 1; hy <= hyres; hy++ )
  {
    cy = ( ( ( double ) hy ) / ( ( double ) hyres ) - 0.5 ) / magnify * 3.0;

    for ( hx = 1; hx <= hxres; hx++ )
    {
      cx = ( ( ( double ) hx ) / ( ( double ) hxres ) - 0.5 ) / magnify * 3.0 - 0.7;

      x = 0.0;
      y = 0.0;

      it2 = itermax + 1;

      for ( iteration = 1; iteration <= itermax; iteration++ )
      {
        x_new = cx + x * x - y * y;
        y_new = cy + 2.0 * x * y;

        x = x_new;
        y = y_new;

        if ( 100.0 < x * x + y * y ) 
        { 
          it2 = iteration; 
          break; 
        }

      }

      if ( it2 < itermax ) 
      {
        color ( 200+(55*it2)/100, (230*(100-it2))/100, (230*(100-it2))/100 );
      }
      else
      {
        color ( 0, 255, 255 );
      }
    }
  }
//
//  Terminate.
//
  return 0;
}
//****************************************************************************80

void color ( int red, int green, int blue )

//****************************************************************************80
//
//  Purpose:
//
//    COLOR writes the R, G and B colors for one pixel.
//
//  Author:
//
//    Eric Weeks
//
{
  fputc ( ( char ) red, stdout );
  fputc ( ( char ) green, stdout );
  fputc ( ( char ) blue, stdout );

  return;
}